In 90 patients with hypercapnic-hypoxemic chronic obstructive pulmonary disease (COPD), noninvasive anthropometric and biochemical nutritional indices were measured to assess the prevalence and features of malnutrition in COPD and to analyze the relationship between nutritional depletion and the severity of the disease. A significant inverse relationship was found between PaCO2 and body weight; a parallel decrease of both somatic proteins and body-energy stores of fat appears to be paired with decreasing body weight. Deterioration of nutritional status occurred in the COPD patients considered despite seemingly adequate calorie and protein intakes, although in patients with more severe impairment of pulmonary gas exchange, calorie intake was significantly lower compared with basal energy expenditure. In the course of hypercapnic-hypoxemic COPD malnutrition is common, it is related to the severity of the disease as judged by the need for hospitalization and degree of impairment of gas exchange, and it may be present despite apparently adequate nutrient intake.