Background and Objective: Obstructive sleep apnea (OSA) is an important risk factor for cardiovascular disorders. The aim of this study was to determine the frequency of OSA in myocardial infarction patients in the CCU of Karaj Hospitals, 2009. Material and Methods: This cross-sectional study was conducted , via convenience sampling , on 140 acute myocardial infarction patients in two cardiac care units of Shariati and Rajaei hospital in Karaj, 2009. We assessed demographic data, history of cardiovascular risk factors, STOP-Bang questionnaire through interview, information related to the type of myocardial infarction and laboratory parameters from medical records, and also we measured anthropometric indices with balance scale and meter tap. Results: Mean score of STOP-BANG questionnaire was 4.9 ± 1.2 in the range of 2 to 8 points and in 64% of the participants was higher than 4 points. The Score of STOP-BANG questionnaire was statistically significant considering age, smoking, hypertension, dyslipidemia, extensive infarction, BMI, waist-to-height ratio, Waist to Hip Ratio, Waist Circumference, neck circumference, cholesterol and left ventricular ejection fraction (P=0.001), sex (P=0.044), Diabetes(P=0.019), inferior infarction (P=0.006), anterior wall (P=0.048) and triglyceride levels (P=0.031). Conclusion: OSA is common among patients with myocardial infarction and is associated with anthropometric indices, cardiovascular risk factors, the location of infarction and left ventricular ejection fraction. Thus, Screening, evaluating the symptoms of OSA and referring for counseling and treatment is necessary.