The malnutrition may exert deleterious effects on every constituent of the respiratory system: respiratory drive, respiratory muscles and pulmonary parenchyma. The occurrence of malnutrition in patients with chronic obstructive pulmonary disease (COPD) is associated with a poor prognosis. However the relationships between nutritional status and ventilatory function remain poorly defined. The malnutrition of COPD patients results mainly from a hypermetabolic state. In undernourished COPD patients, nutritional repletion has been reported to improve the performance of respiratory muscles. In COPD patients with acute respiratory failure, a hypercaloric nutrition may induce ventilatory complications that result mainly from an excessive CO2 production. The use of a lipid-enriched diet has been recently proposed in these patients to facilitate weaning from ventilatory support.