Authors compared cognitive functions in 60 patients (main group) with different stages of discirculatory encephalopathy (DE), I, II and III stages. A comparison group included 10 age-matched normals without DE. All patients underwent a clinical-neurological investigation and performed neuropsychological tests (MMSE, the Clock drawing test, Burdon probe) and Spilberger-Khanin test. Cognitive evoked potentials, including P300, were recorded. Results revealed the decrease in performance on neuropsychological tests and P300 components that indicated the slowing of metabolic processes in the cerebral cells of patients with DE. In patients treated with cytoflavin, the activation of metabolic processes in the brain cells that indicated the protection of the cellular cluster clinically manifested itself in neurocognitive and electrophysiological improvements was observed.