The development of sleep-disordered breathing is common in patients with chronic respiratory insufficiency due to neuromuscular and restrictive disorders, as well as in those with COPD. Nocturnal hypoventilation and obstructive and central apneas result in daytime symptoms of hypersomnolence and fatigue, and contribute to abnormalities in awake gas exchange. Long-term mechanical ventilation, delivered invasively by tracheostomy or more recently by NPPV, has been shown to eliminate sleep-disordered breathing and correct abnormalities in nocturnal gas exchange, resulting in an improvement in sleep quality. Improved daytime symptoms and gas exchange, with the suggestion of a decrease in morbidity and mortality, support the use of long-term mechanical ventilation during sleep in selected patients with these disorders.