BACKGROUND: Diabetes mellitus (DM) is a very well-known risk factor for development of atherosclerosis, and it has been hypothesized that poor glycemic control and hyperglycemia plays a major role in this process. In the current study, we aimed to evaluate the associates of poor glycemic control in Iranian patients who have already undergone coronary artery bypass grafting (CABG), with especial focus on the inhabitation of infectious agents within the coronary arterial wall. METHODS: In January ۲۰۱۰, ۵۲ consecutive patients with type ۲ DM who undergone CABG at the Department of Cardiovascular Surgery of Baqiyatallah University of Medical Sciences (Tehran, Iran) were included into this cross-sectional study and biopsy specimens from their coronary plaques were taken and analyzed by polymerase chain reaction (PCR) methods for detecting Helicobacter species, cytomegalovirus (CMV) and Chlamydia pneumoniae, and their potential relation to the glycemic control status in these patients. RESULTS: Compared to that in diabetic patients with mean fasting blood sugar (FBS) levels FBS < ۱۲۶, atherosclerotic lesions in type ۲ diabetic patients with poor glycemic control (FBS > ۱۲۶) were significantly more likely to be positive for CMV PCR test (۴۱% vs. ۹%, respectively; P = ۰.۰۵). In laboratorial test results, mean triglyceride level was significantly higher among patients of poor glycemic control (۱۶۸ ± ۸۹ vs. ۲۲۲ ± ۱۲۵ mg/dl, respectively; P = ۰.۰۳۳). Hypertension was also significantly more prevalent in this population (۷۳% vs. ۳۶%, respectively; P = ۰.۰۳۴). CONCLUSION: Type ۲ diabetic patients with poor glycemic control can be at higher risk for developing CMV infection in their coronary arterial wall, which can promote atherosclerosis formation process in this patient population. According to the findings of this study, we recommend better control of serum glucose levels in type ۲ diabetic patients to prevent formation/progression of atherosclerosis. Keywords: Diabetes Mellitus, Hyperglycemia, Coronary Artery, Cytomegalovirus, Infection