A large and previously unsuspected population whose breathing is abnormal during sleep has been identified , being healthy by day but may develop upper airway obstruction during sleep . This study aimed at identifying cardiopulmonary changes that occur during sleep in patients with coronary artery disease & to compare these changes to those seen in healthy individuals and those with COPD. It included 50 subjects divided into 3 main groups: 10 healthy volunteers as a control group , 20 subjects with COPD, & 20 subjects with old myocardial infarction (> 6 weeks ) .All 3 groups were subjected to : pulmonary function testing , polysomnography, and echocardiography ( for cardiac subjects only ). Results revealed 30% of cardiac group had sleep stage events changes descriptive of obstructive sleep apnea.Conclusion: sleep disordered breathing is common in patients with coronary heart disease, with an obstructive nature distinct from sleep disordered breathing in heart failure patients & its extent is proportional to infarction size .