The possibility of therapeutic application of hypoxic-hypercapnic mixture of gases (FiO2 — 18 vol.%, FiCO2 — 2 vol.% ) in patients with chronic respiratory failure IInd and IIId stages with moderate arterial hypoxemia. It was demonstrated that inhaling this mixture is accompanied by total and alveolar hyperventilation, causing a reliable increase in oxygenation in this group of patients, not associated with hypocapnia or changes in oxygen blood supply. Concommitantly, there was improvement in the distribution of ventitation-perfusion ratio, physiological pulmonary bypass decreasing by 10—12 % from the initial level, which may account for the above changes. Similar mixture of gases may be recommended in patients with CPF and moderate arterial hypoxemia in order to improve blood oxygenation and to train respiratory system.