Heart function and sleep are closely associated. While NREM sleep reduces cardiac workload, phasic REM sleep increases sympathetic activity and cardiac vulnerability. Heart failure (HF) patients suffer from disturbed sleep due to frequent awakenings, periodic limb movements, sleep apnea, and depression. Insomnia seems to be associated with incident HF, and, when comorbid, results in a vicious circle. There is much evidence of a relationship between breathing disturbances during sleep and heart diseases. At least 50% of HF patients suffer from obstructive (OSA) or central (CSA) sleep apnea, both associated with impaired prognosis. OSA is a risk factor for arterial hypertension, atrial fibrillation, and HF. Continuous positive airway pressure devices reduce adverse cardiac events and improve outcome in severe OSA in compliant subjects. Adaptive servoventilation (ASV) is superior to other therapeutic options for CSA. However, the use of ASV is contraindicated in severe HF with reduced, but not preserved, ejection fraction.