Cardiopulmonary bypass may exacerbate myocardial damage in compromised left ventricles. Early and mid-term outcomes of off-pump coronary artery bypass grafting (OPCAB) vs on-pump coronary artery bypass grafting (On-pump CABG) were compared in patients with poor left ventricular dysfunction, using an analysis of a propensity score matching. Between December 2000 and November 2005, 1,473 patients underwent isolated coronary artery bypass grafting in our institute and 153 patients who had a left ventricular ejection fraction (LVEF) lower than 35% were enrolled. The OPCAB group contained 100 patients and the On-pump CABG group contained 53 patients. Preoperative risk factors were compared and 50 patients in each group were matched. The mean follow-up time was 35.5+/-17.3 months. Three deaths (3.0%) occurred in the matched cohort, with no significant difference between 2 groups. The operation time, ventilation time, intensive care unit admission time and occurrence of respiratory failure were significantly lower in the OPCAB group. The mean LVEF of the 2 groups improved significantly. The overall 6-year actuarial survival rates of the OPCAB and On-pump CABG group were 88.2% and 72.4% (p=0.2), respectively, and there were no significant differences in 6-year rates of freedom from major adverse cardiac and cerebrovascular events (p=0.97). Coronary artery bypass grafting in patients with poor left ventricular dysfunction improved myocardial function. Postoperative respiratory failure was significantly related to the cardiopulmonary bypass for surgical myocardial revascularization. Off-pump and On-pump surgical revascularization resulted in equivalent mid-term outcomes.