Sleep may have several negative consequences in patients with chronic obstructive pulmonary disease (COPD). Sleep is typically fragmented with diminished slow wave and rapid-eye-movement sleep, which likely represents an important contributing factor to daytime symptoms such as fatigue and lethargy. Furthermore, normal physiological adaptations during sleep, which result in mild hypoventilation in normal subjects, are more pronounced in COPD, which can result in clinically important nocturnal oxygen desaturation. The co-existence of obstructive sleep apnea and COPD is also common, principally because of the high prevalence of each disorder, and there is little convincing evidence that one disorder predisposes to the other. Nonetheless, this co-existence, termed the overlap syndrome, typically results in more pronounced nocturnal oxygen desaturation and there is a high prevalence of pulmonary hypertension in such patients. Management of sleep disorders in patients with COPD should address both sleep quality and disordered gas exchange. Non-invasive pressure support is beneficial in selected cases, particularly during acute exacerbations associated with respiratory failure, and is particularly helpful in patients with the overlap syndrome. There is limited evidence of benefit from pressure support in the chronic setting in COPD patients without obstructive sleep apnea.