Diffusion-Weighted Magnetic Resonance Imaging (DW-MRI) is now a powerful tool for functional evaluation of brain tissues. By using Apparent Diffusion Coefficient (ADC) value a sound comparison can be made between different brain parts which otherwise has similar signal characteristics in conventional MRI sequences. The purpose of this study was to investigate the normal ADC values in main cerebral tissues such as grey matter (GM), basal ganglia, white matter (WM), cerebellum and brain stem; we studied changes in ADC with aging. Mean ADC values for 7 different brain structures of 350 normal adult brains were measured, no difference was found according to gender but consistent differences was found between brain structures, and changes with aging found for cerebral white matter and thalamus. This quantitative information may help in better identifying age-related pathology.