Introduction: Obstructive sleep apnea syndrome (OSAS) and coronary artery disease (CAD) are highly prevalent diseases in the population and both appear to be associated. Objectives: This study aimed to identify the clinical characteristics and prevalence of sleep disordered breathing (SDB) and OSAS among CAD patients. Methods: A hundred and thirty-two consecutive patients (111 males and 21 females with mean age of 67.1± 11.5 years, BMI of 27.7 ± 4.5 kg/m2) referred to the Cardiology Division for evaluation of CAD by coronary angiography (CA) were studied. As a first step, the subjects underwent a standard medical interview and general physical examination. Secondly, a sleep questionnaire including questions regarding the history of snoring, breathing pauses during sleep, and excessive daytime sleepiness was applied. The third step was a cardiorespiratory polygraphy that was conducted one or two days before finally carrying out a cardiac catheterization and a CA. Results: 114 patients (86%) presented a positive CA; 18.4% one-vessel disease, 27.2% two-vessel disease and 64.4% three-vessel disease. With respect the SDB levels; 59.1% showed an AHI = 5, 38.6% an AHI = 10; and 21.2% an AHI = 20. In addition, 6.8% reported OSAS (AHI = 5, disrupted breathing during sleep together with excessive daytime sleepiness). The group of patients with AHI = 10 had higher age, BMI and snoring than those patients with AHI < 10. OSAS patients had a higher prevalence of diabetes and hypertension than non-OSAS patients. In addition, OSAS patients had lower left ventricular ejection fraction. No significant differences among groups were observed in the number of coronary vessels affected. Conclusion: SDB and OSAS are very common among coronary disease patients and may be associated to left ventricle performance. This finding suggests the need for physicians to perform routine screening and individual evaluation of coronary patients for sleep-disordered breathing.