Objective: To determine whether the percentile quantification of emphysema with computed tomography has a stronger association with pulmonary complications than pulmonary function testing after pulmonary lobectomy. Methods: The patients who underwent pulmonary lobectomy and also had thin-section chest computed tomography scans available from July 2009 through August 2011 were reviewed. The patients were divided into 2 groups according to whether they had a history of chronic obstructive pulmonary disease. The emphysema index (EI) was defined as the volumetric percentage of the areas of low computed tomography attenuation, which was measured using automatic analysis software. Receiver operating characteristic curve analysis was used to compare the predictability of pulmonary complications, and multivariate analyses were performed to determine the risk factors for pulmonary complications. Results: A total of 280 patients were evaluated. Pulmonary complications occurred in 37 patients (13.2%). The median EI was 9.30 (range, 0.04-37.27). The area under the receiver operating characteristic curve was significantly greater for the EIs than for the pulmonary function testing values. The cutoff EI value was 11.46, and the sensitivity and specificity was 83.8% and 74.1%, respectively. EI, male gender, and diffusing capacity < 80% were risk factors for pulmonary complications for all patients; EI and age > 70 years were risk factors for patients without chronic obstructive pulmonary disease; and EI and diffusing capacity < 80% were risk factors for patients with chronic obstructive pulmonary disease. Conclusions: The EI is a significant risk factor for pulmonary complications after pulmonary lobectomy and had stronger association with them than did pulmonary function testing. The EI might serve as a useful tool for evaluating risk before pulmonary lobectomy.