The main aim of this research was to determine inter-positional and intra-positional differences in some anthropometric characteristics of young female volleyball players. The subject sample included 204 female youth volleyball players from whole Croatia, who participated in the open Croatian volleyball championship in 2014. Mean chronological age of the subjects was 14.11±0.84 years, indicator of biological age was 14.12±0.76 years and average training experience was 42.14±16.76 months. The independent variable set in this research consisted of 11 anthropometric measures, 10 motor tests and 3 questionnaires of psychological characteristics (hope, optimism and perfectionism). The following anthropometric measures were measured: body height, sitting height, body mass, elbow diameter, knee diameter, upper arm circumference flexed, calf circumference, triceps skinfold, back skinfold, abdominal skinfold and calf skinfold. From these characteristics the following were calculated: body mass index, somatotype according to the Heath-Carter method and peak height velocity (PHV. Based on the deviations of PHV values of each subject from the average PHV value of all the subjects, and by adding or subtracting the obtained deviations from chronological age, the indicator of biological age of young female volleyball players was calculated. Among motor tests for assessing non-specific agility and explosive power, the following tests were applied: side steps, 9-3-6-3-9, standing long jump, supine medicine ball throw and 20-m sprint; and for assessing specific agility and explosive power, the following tests were applied: step hop test, standing vertical jump and spike approach volleyball jump and spiking speed from the ground and from the net. In the space of psychological characteristics, the Life Orientation Test – Revised was applied to assess optimism, the Children Hope Scale was applied to assess hope, and the Sport Multidimensional Perfectionism Scale was applied to assess perfectionism. Dependent variables in this research included player role and competitive efficacy. The subjects were divided into 5 sub-groups according to their player roles: setter, opposite hitter, passer-hitter, middle blocker and libero players. According to team placement in the competition and quality of each player in their team, volleyball players were divided into two groups: more efficient and less efficient. High values of inter-item correlation and low values of coefficients of variation indicate that all the anthropometric variables have a high level of relative and absolute reliability. Good homogeneity of all the anthropometric measures was determined by the dependent samples T test. All the applied tests for assessing motor abilities have a high level of absolute and relative reliability. Out of the motor tests applied, only the 20-m sprint test has satisfactory homogeneity. In most other tests for assessing motor abilities a trend of result improvement during the three performances of the test was noticed, probably due to the insufficient number of trials. In tests assessing spiking speed from the ground and from the net by radar, a deterioration of results was noticeable during the repeated performance, which is probably the consequence of fatigue due to insufficient rest periods between repetitions, or loss of concentration due to imprecision in previous attempts. By analysing the metric characteristics of psychological characteristics, satisfactory reliability of all the scales was determined, except optimism which showed a limit level of reliability. The hope questionnaire, as well as the scales of personal standards, perceived coach pressure and doubts about actions from the questionnaire assessing sport perfectionism have good homogeneity. The questionnaire assessing optimism, alike the rest of the scales of the Sport Multidimensional Perfectionism Scale (concern over mistakes, perceived parental pressure and organization), showed good homogeneity only after selecting (excluding) one to two items. The sensibility of anthropometric, motor and psychological variables was assessed by comparing the obtained values of the Kolmogorov-Smirnov test with the limit values, and additionally by analysing the coefficients of distribution Skewness and Kurtosis if the KS test values were above the critical value. It was determined that sensitivity of all the scales except perceived parental pressure from the sport perfectionism questionnaire is satisfactory. Given that this scale had by far the lowest means, which indicates that the subjects – young female volleyball players do not have high expectations set by their parents, it too was kept in the set of measures for further application of statistical procedures. By discriminant analyses on the overall subject sample (regardless of position), it was determined that more efficient volleyball players are taller and heavier, and did better in all the tests assessing motor abilities in comparison to less efficient players. Even though discriminant analysis in the space of psychological characteristics did not find significant differences between more efficient and less efficient volleyball players, by analysing the mean values it can be noticed that more efficient volleyball players have a higher level of optimism and hope, and a lower level of sport perfectionism. By analysing the means of subjects’ biological age, inter-positional and intra-positional differences were found. Liberos (13.70 years) and setters (13.82 years) are biologically the youngest. Opposite hitters (14.17 years) and passer-hitters (14.21 years) are somewhat biologically older. Middle blockers are biologically the oldest (14.54 years). More efficient players at all positions are also biologically the oldest. These differences range from averagely 3-5 months (setters, liberos and passer-hitters) to almost a year (opposite hitters and middle blockers). To neutralise the influence of biological age on inter-positional and intrapositional differences of young female volleyball players in the variables assessing morphological characteristics, motor abilities and psychological characteristics, analyses of covariance are applied with the indicator of biological age variable as covariate. Based on inter-positional differences in anthropometric measures it can be inferred that middle blockers are significantly taller than the other player positions, whereas libero players are the shortest, followed by setters. Liberos and setters are the most endomorphic, liberos are the most mesomorphic, and opposite hitters and middle blockers are the most ectomorphic. By analysing the inter-positional differences in proportions of separate somatotype categories it was determined that passer-hitters do not differ from setters and liberos. Libero players have a significantly higher proportion of the endomorphicmesomorph category in comparison to other player roles. Middle blockers and opposite hitters have a significantly higher proportion of the balanced ectomorph category than setters and liberos. In the overall sample, as well as the subsample of more efficient players, passer-hitters have the best results in most motor tests. Efficient setters and liberos are characterized by good performance of agility tests, and compared to the other player positions they have somewhat lower average results in spiking speed. There are no inter-positional differences in psychological characteristics. Among the anthropometric measures, the indicator of biological age significantly affects the inter-positional differences in height, body mass and body mass index in the overall sample, whereas in a more homogenous sample of more efficient volleyball players it does not affect the inter-positional differences. In the overall sample the indicator of biological age affects inter-positional differences in all the variables, and in the subsample of more efficient volleyball players in most variables. In the space of psychological characteristics the indicator of biological age does not affect inter-positional differences neither in the overall sample nor in the subsample of more efficient players. By analysis of covariance in the space of anthropometric measures only one significant intrapositional difference is found. More efficient setters are significantly taller than less efficient ones. There are no significant differences in proportions of separate somatotype categories between more efficient and less efficient female volleyball players with different player roles. More efficient setters, passer-hitters and opposite hitters did better in most tests assessing motor abilities in comparison to less efficient players at the same position. The differences are most prominent in tests assessing spiking speed. At libero position, more efficient players are significantly better than less efficient players only in the performance of side steps, and at middle blocker position, more efficient players are better only in the two tests assessing spiking speed. There are no significant intra-positional differences in psychological characteristics found for player positions of setters and opposite hitters. More efficient passer-hitters have a lower perception of parental expectations and coach pressure than less efficient players at the same position. The hope variable is significantly higher in more efficient middle blockers, and optimism and hope variables are significantly more expressed in more efficient libero players, whereas their perfectionism – organization variable is significantly less expressed than in less efficient liberos. In all player positions the indicator of biological age significantly affects intra-positional differences in body height and body mass between more efficient and less efficient female volleyball players. Additionally, it affects intra-positional differences in the endomorph somatotype component in setter position, whereas it affects the mesomorph somatotype component in middle blockers. In the motor abilities space the indicator of biological age as covariate significantly affects the intra-positional differences in most of the motor abilities. The setters are the exception as this effect is found only in the supine medicine ball throw variable. In the psychological variables space the indicator of biological age affects intrapositional differences in the organization variable in liberos and middle blockers, the hope variable in middle blockers and opposite hitters, and perceived parental pressure and perceived coach pressure variables in passer-hitters. The obtained results have great importance for understanding and improving the process of detection, identification and development of young female volleyball players. Given that the influence of biological age on their inter-positional and intra-positional differences in the applied variables was proven, there is a real danger of underestimating the ultimate possibilities of biologically younger players in that process. This could finally result also in their premature withdrawal from sport.