Static lung volumes, lung elasticity, and airway patency indices were measured in 47 children operated on for ventricular septal defect (VSD). Open-heart surgery was performed at the age of 0.6-12.0 years (median 4.1 years). In the first group (34 subjects), after primary repair of the VSD, there was an increase in lung recoil pressure at 100% of total lung capacity (TLC) (128% of the predicted value) and a reduction in specific airway conductance (sGaw) (75% of the predicted value). In the second group (13 patients), who had had previous pulmonary artery banding at 0.2-4.0 years (median 0.7 year) there was an increased functional residual capacity/TLC ratio (111% of predicted value), reduced sGaw (69% of predicted value), and reduced maximum expiratory flow at 25% of vital capacity (79% of predicted value). Lung volumes were insignificantly reduced in both groups. The frequency of lung function disturbances was similar in the two groups (71% of patients in the former group and 77% of patients in the latter group). A linear positive correlation between specific airway conductance and the mean pulmonary artery pressure (mPAP) (r = 0.793, p < 0.006) was observed in children with an mPAP <30 mmHg prior to open-heart surgery. A positive correlation between static recoil pressure at full inflation and mPAP (r = 0.545, p < 0.03) was found in children with an mPAP > 30 mmHg. The severity of congenital heart disease prior to surgery and the influence of the timing of the surgical procedures may cause the differences in lung function tests between the groups.