OBJECTIVE We determined whether minimally invasive direct coronary artery bypass (MIDCAB) leads to excellent postoperative pulmonary function, and which contributes more to this--minithoracotomy or avoidance of cardiopulmonary bypass. METHODS Pulmonary function 1 week before and 2 weeks after surgery was evaluated in 8 patients undergoing MIDCAB (Group M), 10 undergoing off-pump coronary artery bypass (Group O), and 12 undergoing conventional coronary artery bypass grafting (Group C). Parameters were adjusted by their predicted values and postoperative values were expressed as a ratio to preoperative ones. RESULTS Only Group M maintained postoperative vital capacity and forced expiratory volume in 1 second close to the preoperative level and thus, showed significantly better recovery than Groups O and C. No significant difference was seen between Groups O and C. CONCLUSIONS MIDCAB provides better recovery of pulmonary function early postoperatively than other procedures thanks to minithoracotomy rather than avoidance of cardiopulmonary bypass.