Abstract Objectives: To set age-specific normal reference values for brainstem, cerebellar ‎vermis, and peduncles measurements and characterize values’ variations according to ‎gender, age, and age by gender interaction.‎ Methods: 565 normal brain magnetic resonance examinations with normal anatomy ‎and signal intensity of the supra- and infratentorial structures were categorized into six ‎age groups (infant, child, adolescent, young adult, middle-age adult, and old aged ‎adults). Patients with congenital malformations, gross pathology of the supra- or ‎infratentorial brain, brain volume loss, developmental delay, metabolic disorders, and ‎neuropsychological disorders (n = 2.839) were excluded. On midsagittal T1 weighted ‎and axial T2 weighted images specific linear diameters and ratios of the brainstem, ‎cerebellar vermis, and peduncles were attained. Two observers assessed a random ‎sample of 100 subjects to evaluate the inter and intraobserver reproducibility. Intraclass ‎correlation coefficients, means ± standard deviation, one and two-way analysis of ‎variance tests were used in the statistical analysis.‎ Results: Good to excellent inter- and intraobserver measurements’ reproducibility were ‎observed, except for the transverse diameter of the midbrain, the anteroposterior ‎diameter of the medulla oblongata at the pontomedullary and cervicomedullary ‎junctions, cerebellar vermis anteroposterior diameter, and thickness of the superior ‎cerebellar peduncle. Age-specific mean values of the investigated measurements were ‎established. A significant gender-related variation was recorded in the anteroposterior ‎diameter of the basis pontis (p = 0.044), the anteroposterior diameter of the medulla ‎oblongata at the cervicomedullary junction (p= 0.044), and cerebellar vermis height (p = ‎‎0.018). A significant age-related change was detected in all measurements except the ‎tectal ratio. Age by gender interaction had a statistically significant effect on the tectal ‎ratio, inferior, and middle cerebellar peduncles’ thickness (p = 0.001, 0.022, and 0.028, ‎respectively).‎ Conclusion: This study provides age-specific normal mean values for various linear ‎dimensions and ratios of the posterior fossa structures with documentation of ‎measurements’ variability according to gender, age, and their interaction.‎ Advances in knowledge: It provides a valuable reference in the clinical practice for ‎easier differentiation between physiological and pathological conditions of the posterior ‎fossa structures especially various neurodegenerative diseases and congenital anomalies.‎