The article discusses the features of sleep disorders in patients with Lewy body dementia and Parkinson’s disease. The focus is on behavioral disorders during the rapid eye movement phase, which are manifested by active movements and aggressive sleep behavior, as well as other sleep disorders, such as insomnia and excessive daytime sleepiness. The mechanisms of development of these disorders and their impact on the quality of life of patients and their relatives are described. Current approaches to diagnosing and treating these conditions, including pharmacotherapy and non-drug correction methods, are discussed.