Abstract: Introduction: Type 2 diabetes mellitus (DM2) is a metabolic disorder that is one of the most common diseases in our country and in the world, the most frequent complication of which is cerebrovascular diseases, which lead to a persistent decrease in the quality of life of the patient and his relatives, the problem of diagnosis of which occupies one of the central places in modern neurology. Objective: to study changes in the level of AAT to protein S 100 and markers of endothelial dysfunction in patients suffering from DM 2. Materials and methods: To study the root cause of the central forms of diabetic neuropathy, a comprehensive examination of 81 patients with chronic cerebral ischemia and type 2 diabetes mellitus was conducted with an assessment of markers of endothelial dysfunction and oxidative stress, a study of the level of nitrites and the total indicator of antioxidant activity, determination of the concentration of autoantibodies to protein S 100 in blood plasma. Results: The serum malondialdehyde index was changed to the greatest extent in patients with moderate cognitive impairment. An increase in the concentration of autoantibodies to the S 100 protein was revealed in the presence of mild and moderate cognitive impairment. The maximum increase in the concentration of autoantibodies to the S100 protein was detected in patients with type 2 diabetes mellitus with moderate cognitive impairment. Discussion: In a comparative analysis of patients, it was found that in patients suffering from cognitive impairment, an increase in serum peroxidation processes was noted in comparison with the indicators of patients without cognitive dysfunction. Conclusions: The revealed changes in immunological and biochemical research methods demonstrate the pathogenetic role of oxidative stress in the formation of cognitive impairment in patients with type 2 diabetes mellitus, manifested by an increase in the concentration of autoantibodies to the S 100 protein.