The aim of this paper is to classify the levels and structures of motor and morphological specifics, which affect the overall stability index coefficient (OSI) using Biodex Balance System. A sample of 31 boys aged 12, 05 ± 1, 51 were classified into three qualitative groups by the OSI mean and standard deviation (SD) results. Multivariate analysis of variance (MANOVA) revealed the existence of differences and statistical significance in morphological and motor abilities between groups. Based on the results of MANOVA there is a highest level of significance when classifying into the groups. Univariate F test found the greatest difference between the groups in variable of body mass (AMAS, p – 0,003). Leven’s test for heterogeneity of variance determined differences between groups in: body height (AVIS, p – 0,01); lengthwise standing on the balance bench with left foot (MRUUL, p – 0,037); lengthwise standing on the balance bench with right foot (MRUUD, p – 0,003); lengthwise standing on the balance bench with both feet (MRUB, p – 0). LSD post hoc test found differences between two groups in three ball slalom with feet (MKP3N, p – 0,045) and agility assessing test (MTTEST, p – 0,034). The results of the research can be used for selecting and choosing talented boys for complex sports, in which dominates agility, coordination and balance, while using the stability index coefficient, height and weight.