There are more and more studies that focus on cognitive decline in patients with chronic obstructive pulmonary disease (COPD). Obstructive sleep apnea syndrome (OSAS) is characterized by a repetitive cessation or decrease in airflow due to upper airway obstruction. Chronic sleep disturbance and intermittent hypoxemia lead to neurocognitive changes. Patients with comorbidity of COPD and OSAS may develop more severe nocturnal hypoxia than those with OSAS or COPD alone. At the same time, cognitive dysfunction in elderly patients with comorbidity of OSA and COPD has not been previously studied. Objective. The study the effects of OSAS on cognitive impairment and quality of life in elderly patients with COPD. Materials and methods. We examined 84 patients with COPD of moderate severity, controlled course at the age of 60–74 years (mean age – 66.3±4.1 years), of which the first group consisted of 43 patients with COPD, the second group – 41 patients with COPD and OSA of moderate severity. Results. Patients with COPD and moderate OSA had worse MMSE and EQ-5D-3L scores compared to patients with COPD alone, and were more likely to have dementia on the MMSE scale (MMSE≤24 scores), which may require an individual approach to the treatment of such patients.