Background. Inhaled nitric oxide is a highly selective pulmonary vasodilator, the potential benefits of which include reduced resistance and pressure in the pulmonary artery without systemic arterial hypotension, vasodilation in well-ventilated areas of the lungs, rapid onset of action, and a fairly low incidence of side effects in the therapeutic dose range. Objective. Тс estimate the clinical efficacy and safety of the method for synthesizing nitric oxide from room air in the postoperative period of cardiac surgery. Design and methods. A total of 110 patients were enrolled in the study: 55 patients were included in the main group (nitric oxide was synthesized from room air by AIT-NO-01 device), 55 patients were enrolled in the retrospective control group (nitric oxide was inhaled from the balloon). Inclusion criteria were: undergone heart surgery, mean pulmonary artery pressure (PAPm) ≥ 25 mm Hg., pulmonary artery wedge pressure (PAWP) ≤ 15 mm Hg. Results. After one hour of nitric oxide inhalation in the main group, there were a 35 % decrease in PVR and a 16 % decrease in PAPm. In the control group, there were a decrease in PVR by 40 % and decrease in PAPm by 19 %. Inhalation of nitric oxide did not affect the systemic circulation hemodynamics both in the main and in the control groups. The median duration of the mechanical ventilation (MV) was 7.3 (4.5; 13.8) h and the median length of stay (LOS) in the ICU was 23.2 (21.3; 46) h in the main group. In the retrospective control group, the median duration of MV was 8.2 (5; 14.1) h, and the length of ICU stay was 24 (22; 45.3) h; found no differences between the groups. Conclusion. Nitric oxide synthesized from room air significantly reduces PVR and PAPm in patients with precapillary pulmonary hypertension after cardiac surgery. There were no significant differences in the effect on a pulmonary circulation, clinical data and side effects between the methods of synthesis of nitric oxide from room air and dosing from balloons.