This study was designed to compare the effects of preoperative and postoperative incentive spirometry on lung functions after laparoscopic cholecystectomy in 50 otherwise normal healthy adults. Patients were randomized into a control group (group PO, n=25) and a study group (group PR, n=25). Patients in group PR were instructed to carry out incentive spirometry before the surgery 15 times, every fourth hourly, for 1 week whereas in group PO, incentive spirometry was carried out during the postoperative period. Lung functions were recorded at the time of preanesthetic evaluation, on the day before the surgery, postoperatively at 6, 24, and 48 hours, and at discharge. Significant improvement in the lung functions was seen after preoperative incentive spirometry (group PR), P<0.05. The lung functions were significantly reduced till the time of discharge in both the groups. However, lung functions were better preserved in group PR at all times when compared with group PO; P<0.05. To conclude, lung functions are better preserved with preoperative than postoperative incentive spirometry.