Chronic cerebrovascular diseases (CVD) and neurodegenerative diseases (NDD) are the most common causes of cognitive impairment (CI). The development of dementia is preceded by mild CI (MCI) over several years.Objective: to investigat the effect of inhaled nitric oxide therapy on cognitive function (CF) in patients with MCI due to CVD and NDD.Material and methods. The study included 94 patients (25 men and 69 women aged 50 to 76 years, mean age 65.3±8.9 years) with MCI due to CVD and/or NDD of the brain. The patients were randomized into two groups: the main group (therapy) and the control group. The control group comprised 22 patients with MCI (5 men and 17 women aged 50 to 76 years, mean age 62.3±8.5 years) who received standard therapy (antihypertensive, antithrombotic and other agents). The main group comprised 72 patients (20 men and 52 women aged 50 to 76 years, mean age 66.2±8.0 years) who additionally inhaled a nitric oxide-enriched air mixture for 30 minutes daily using the Tianox device. Each patient had from 7 to 10 inhalation sessions (the first trial session lasted 20 minutes, the following sessions 30 minutes). Neuropsychological tests, emotional state and sleep quality were examined at the beginning and 3 and 6 months after the end of treatment. Results. In the main group, after 3 and 6 months, a significant (p<0.05) improvement in CF was found according the Montreal Cognitive Assessment (MoCA-test), Frontal Assessment Battery, the Digit Forward and Backward Span Test, the Digit Symbol Substitution Test, the Munsterberg Test, the Literal Association Test and the 12-word Delayed Free Recall Test. A significant (p<0.05) decrease in anxiety and depression according to the Hospital Anxiety and Depression Scale, the Beck Depression Inventory and the Spielberger Anxiety Scale as well as an improvement in sleep quality according to the Insomnia Severity Index were also observed. The therapy was well tolerated, and no serious adverse events occurred. No significant improvement in CF, emotional state or sleep was observed in the control group.Conclusion. Brief therapy (7–10 sessions) with inhaled nitric oxide improves the CF and emotional state of patients with MCI on a background of CVD and NDD. Further studies on inhaled nitric oxide therapy in patients with MCI in a multicenter randomized trial with sham treatment are needed.