During the past 25 years, we came across 60 patients with corticotroph pituitary adenomas and Cushing's disease. Neuroradiological examination showed prominent volume loss of the brain parenchyma, unexpected for the patient's age. This "brain atrophy" appeared to regress after surgical removal of pituitary adenoma and normalization of cortisol level. Observed difference between degree of "brain atrophy" in the Cushing's disease group and in the control group was statistically significant (p < 0.001). The degree of "brain atrophy" correlated well with the duration of Cushing's disease. Partial reversibility of "brain atrophy" was noticed during the 2nd, 3rd and 4th year after surgery and normalization of cortisol level. Increased cortisol level is one of the causative factors in pathogenesis of "brain atrophy". Loss of brain volume is at least partially reversible after normalization of cortisol levels.