Bilingualism is widespread in the world and In Russia and in recent years has been actively considered within the framework of the cognitive reserve concept. The paper provides a review of articles studying cognitive functions in bilingual patients with neurological diseases. Cognitive disorders and dementia in bilinguals occur about 5 years later in comparison with those who speak only one language. However, when morphological changes in the brain overcome the critical threshold, dementia progresses faster than in monolinguals. The frequency of aphasia in post stroke bilingual patients does not differ from that of monolinguals, but the recovery of speech disorders occurs faster in the former. It is shown that the advantages of bilinguals in the cognitive sphere are provided by executive functions, which is associated with the constant need to switch from one language to another. In single studies, these data have been confirmed in patients with epilepsy. Bilingualism may be promising in the context of reducing the risk of cognitive impairment. Further research of the effect of bilingualism on cognitive status in various pathologies of the nervous system is needed.