Neuropsychological and PET-FDG examination and assessment with the EDSS scale in patients with different types (relapsing-remitting or progressive) of multiple sclerosis (MS) were performed in order to determine the relationship between cognitive impairment and changes in the regional cerebral metabolic rate of glucose (rCMRglu) in the brain gray matter. A study included 61 patients with relapsing-remitting (n=38) and progressive (n=23) types of MS. A statistical analysis revealed significant correlations between cognitive impairment and rCMRglu dependent on the type of MS. The changes in the functional activity of the brain gray matter during the progression of the disease and increasing disability were identified.