Abstract： Objective To explore the impact of obesity on postoperative morbidity and mortality after pneumonectomy. Methods Clinical data of 3 494 patients with pulmonary diseases who underwent pneumonectomy in Shanghai Pulmonary Hospital from September 2003 to December 2007 were retrospectively analyzed. All the 3 494 patients were divided into two groups according to the patients’ preoperative body mass index （BMI）. There were 3 340 patients in the non-obesity group （BMI＜28 kg/m2） including 2 502 males and 838 females with their average age of 61.9±10.7 years， and 154 patients in the obesity group （BMI≥28 kg/m2） including 87 males and 67 females with their average age of 59.7±9.6 years. Univariate analysis and logistic regression were used to analyze the impact of obesity （BMI≥28 kg/m2） on postoperative morbidity after pneumonectomy. Results There were a total of 26 cases of perioperative death， including 23 patients in the non-obesity group and 3 patients in the obesity group. There was no statistical difference in mortality between the two groups ［0.7% （23/3 340） vs. 1.9% （3/154）， P=0.118］. There was no statistical difference in any particular postoperative morbidity or incidence of pulmonary complications between the two groups （P＞0.05）. Other than pulmonary complications， the incidence of postoperative complication in other body systems of the obesity group was significant higher than that of the non-obesity group （P＜0.05）. The incidence of cerebrovascular accidents， myocardial infarction and acute renal failure of the obesity group was significant higher than those of the non-obesity group （P＜0.05）. Logistic regression showed that obesity （BMI≥28 kg/m2） was not an independent risk factor for postoperative morbidity after pneumonectomy ［B=0.648， OR=1.911， 95% CI（0.711， 5.138），P=0.199］. Conclusion Obesity is not a significant risk factor of postoperative mortality or morbidity after pneumonectomy.