Air leaks are a common complication of pulmonary resection. The aims of this study were to analyze risk factors for postoperative air leak and to evaluate the role of air leak measurement in identifying patients at increased risk for cardiorespiratory morbidity and prolonged air leak. From March to December 2009, 142 consecutive patients underwent pulmonary resection for malignancy and were prospectively followed up. Preoperative and intraoperative risk factors for air leak were evaluated. Air leaks were qualitatively and quantitatively labeled twice daily. There were 52 (36.6%) patients who had an air leak on day 1, and 32 (22.5%) who had an air leak on day 2. Air leak was ≥180 ml/min in 12 (37.5%) of these patients. Independent predictors of air leak on day 2 included type of pulmonary resection, presence of adhesions, and incomplete fissures. Cardiorespiratory morbidity was significantly higher (34.4%) in patients who experienced air leak on day 2 than in those who did not (10.9%) (P=0.002). Nine (75%) out of 12 patients with air leak ≥180 ml/min on day 2 had prolonged air leak (greater than five days) (P=0.0001).