RELEVANCE. This article is devoted to the study of the effect of the level of daily physical activity on the functional state, cognitive performance and quality of life of patients with central nervous system tumors and brain metastases. Even though brain tumors make up a relatively small percentage of all malignant neoplasms, they have a significant negative impact on the physical and mental health of patients. AIM. Assessment of the impact of the level of daily physical activity on cognitive functions, exercise tolerance, and quality of life in patients with tumors of the central nervous system or metastases of tumors of other locations in the brain. MATERIALS AND METHODS. The study involved 30 patients suffering from a primary brain tumor or having brain metastases from tumors of other localizations. To assess physical functioning, the Rivermead Mobility Index, Short Physical Performance Battery (SPPB), the "clock test" for assessing cognitive functions and a specialized FACT-Br questionnaire for assessing quality of life were used. RESULTS AND DISCUSSION. According to the results of the study, 30% of patients regularly played sports before the disease manifestation, but only half of them maintained a high level of daily activity during antitumor therapy (55.5% of men; 50% of women). According to objective indicators (Rivermead index and SPPB), patients maintained a moderate level of functional activity. A statistically significant positive correlation was noted between physical condition (SPPB, Rivermead) and cognitive functions (clock test). Quality of life assessment (FACT-Br) revealed a significant decrease in physical and emotional well-being, as well as pronounced problems associated with the disease, which is reflected in the low overall FACT-Br index. CONCLUSION. Brain tumors have a significant negative impact on the physical and mental health of patients. Maintaining a high level of physical activity is associated with improved mobility, cognitive function, and quality of life. This effect is thought to be due to modulation of biological processes, in particular, increased levels of neurotrophic factors that promote neuroplasticity and recovery. Incorporation of physical exercise into complex therapy represents a promising approach to improve clinical outcomes and reduce the severity of symptoms. Further research is needed to optimize physical rehabilitation programs and to better understand the mechanisms by which physical activity influences the course of the disease and prognosis.