Sleep in chronic obstructive pulmonary disease (COPD) is commonly associated with oxygen desaturation, which may exceed the degree of desaturation during maximum exercise, both subjectively and objectively impairing sleep qualities. Coexistence of COPD and obstructive sleep apnea (OSA), referred to as overlap syndrome, has been estimated to occur in 1% of the general adult population. Treatment with continuous positive airway pressure alleviates hypoxemia, reduces hospitalization and pulmonary hypertension, and improves survival. The respiratory effects of sleep in patients with COPD, including a diagnostic approach and treatment to sleep-disordered breathing in this population, will be presented here.