Changes in pulmonary function and the development of atelectasis in the postoperative period have been well documented in the adult population. The use of incentive spirometry has been shown to be effective in the prevention of these postoperative complications. At the Hospital of Sick Children, we studied 17 children (8 control and 9 study) to determine if the same trends occurred. Baseline and follow-up roentgenograms and pulmonary function tests (PFTs) were documented for both groups. In addition, the study group followed the protocol for incentive spirometry. There was significantly less atelectasis in the study group (33%) than in the control group (88%). There was a significant loss of pulmonary function postoperatively in both groups. However, there were no statistically significant differences between the groups either in the degree of pulmonary function loss postoperatively or in the recovery baseline pulmonary function to discharge. We conclude that incentive spirometry is as effective in reducing the incidence of atelectasis in children undergoing cardiac surgery as in adults.