Objective: The objective of this paper is to present possible differences in spondylometric dimorphic characteristics of lumbar spine in the period of progressive development. Material and methods: The research material included 24,517 individuals of both sexes aged from 3 to 25. Individuals that showed abnormal structure of the motor system and individuals reporting pain in the joints of the spine were excluded. Spondylometric research was carried out using the Penny & Giles electrogoniometric measuring system. Significance tests concerning position measurements (Student's t-test, Welch's t-test) were used as well as biometric profiles formed on the basis of Mollison index for each characteristic in the studied period of ontogenesis. The progress of development of the examined spondylometric characteristics in both sex groups was calculated on the basis of expressing the size of the feature in successive age groups as a percentage of its final size. Using the linear and polynomial regression models, the developmental lines of the studied spondylometric parameters were obtained in males and females. Results: In the development process of the studied spondylometric parameters, dimorphic diversity can be observed essentially only in adolescence. In general, in the whole studied period of ontogenetic development, the greater range of lumbar spine mobility is found in females. Minor sexual dimorphism is also evident in the dynamics of development and in the stage of development of the majority of examined characteristics in individual age ranges in relation to the final values, for the benefit of the female sex.