The three main dimensions of quality of life (physical function, social activities, and psychological status) were evaluated by a questionnaire in 41 COPD patients with severe respiratory failure treated by long-term oxygen. The results were compared with those obtained in patients suffering from COPD without chronic respiratory failure and in patients suffering from severe diabetes and/or atherosclerosis. A relevant impairment of the indexes of quality of life was found in the group of subjects with chronic respiratory failure. The extent of the impairment was significantly higher in these subjects than in the two other groups of patients.