Objective:Compare the prognosis and complications of diabetic and non-diabetic patients undergoing isolated coronary artery bypass surgery at a hospital with a high surgical volume.Methods:Data of patients who underwent coronary artery bypass surgery from June 2009 to July 2010 were analyzed. We selected diabetic and non-diabetic patients and evaluated their postoperative and long-term prognosis based on clinical complications. To reduce the disparity within the sample, statistical analyses were performed using propensity scores.Results:We included 2,688 patients who underwent coronary artery bypass surgery; 36% of them had diabetes, their mean age was 62.1±9.49 years and 70% (1,884) of them were men. Patients with diabetes were older (63±9 years vs. 61±10 years; P<0.001), more often obese (BMI>25 kg/m2: 70.7% vs. 64.5%; P<0.001), dyslipidemic (50.4% vs. 41.1%; P<0.001), hypertensive (89.2% vs. 78.7%; P<0.001), and presented chronic renal failure (8.3% vs. 3.8%; P<0.001). They also presented higher rates of acute renal failure (5.6% vs. 2.7%, P<0.001), infection (11.4% vs. 7.2%, P<0.001) and mortality after one year (9.1% vs. 5.6%, P<0.001). Pneumonia was more common among patients with diabetes (7.7% vs. 4.0%, P<0.001). According to propensity scoring, 430 patients (215 diabetics and 215 non-diabetics) had a mean age of 61.3±8.97 years, and 21.2% (91 of 430) were women. However, diabetes was not an independent factor for poor prognosis.Conclusion:Patients with diabetes were at higher risk for postoperative complications and mortality after undergoing coronary artery bypass surgery. However, diabetes did not explain the poor prognosis of these patients after pairing this factor with the propensity score.