BACKGROUND Minimally invasive direct coronary artery bypass (MIDCAB) requires substantially smaller incisions than conventional coronary artery bypass grafting (CABG). We investigated whether this fact may lead to less postoperative pain and improved pulmonary function. METHODS Preoperative and postoperative (days 1, 3, and 5) pulmonary function and postoperative pain were assessed in 15 patients undergoing MIDCAB (group A) by using a standardized score and were compared with 15 patients admitted for CABG (group B). RESULTS Total operation time (140 minutes versus 189 minutes; p<0.001) and duration of mechanical ventilation (300 minutes versus 840 minutes; p<0.001) were significantly less in group A. Pulmonary function was comparable between the 2 groups on postoperative day 1 (POD 1). Vital capacity was significantly greater in group A on POD 3 (59.7% versus 40.6%; p<0.001) and on POD 5 (74.4% versus 53.9%; p<0.001). Similar results were found for forced expiratory volume in 1 second (group A versus B on POD 3: 56.3% versus 42.2%; p<0.05; and on POD 5: 68.4% versus 55.5%; p<0.01). Postoperative pain was significantly higher in group A (POD 1: score 5.5 versus 3.6; POD 3: 4.0 versus 2.9; p<0.01). CONCLUSIONS MIDCAB procedures lead to better preservation of pulmonary function compared with conventional CABG despite greater postoperative pain.