Objective To compare the lung volume before and after the operation for the treatment of chronic empyema with CT 3-dimensional imaging,and to evaluate its role in the assessment of pulmonary function. Methods A total of 78 patients with chronic empyema from 2000 to 2016 in our hospital were enrolled in this study.The patients were divided into two groups according to the operational styles,with 47 cases in the decortication group and 31 cases in the catheter drainage group respectively.Reformation of the chest CT data was used to determine the lung volumes and the routine pulmonary function tests(PFT)were performed before and after the operation. The lung volumes and the PFT results before and after the operation were compared between the two groups with t test. Then multiple linear regression analysis was applied to test the relationship between the lung volumes and the values of PFT after the operation. Results The mean lung volume of catheter drainage group was(1 548±467)cm3,while it was(1 418±802) cm3for the decortication group preoperatively(t=1.665,P=0.07).After the operation,the mean lung volume of decortication group was(2 677±815)cm3,while it was(2 169±185)cm3for the catheter drainage group. There was statistically significant difference for the increase of lung volume between the two groups after operation(t=2.371,P<0.05).There was no significant difference between the two groups before the operation for the values of the PFT(t=1.467 to 1.874,P>0.05). After the operation, the values of the PFT in the decortication group were higher than those in the catheter drainage group(t=1.990 to 2.799, P<0.05). The changes of postoperative lung volume were positively correlated with the values of the PFT(β=0.312 to 0.701,P<0.05). Conclusions Decortication has a better effect on the lung volume and the pulmonary function for patients suffered from chronic empyema. CT modeling (3-dimensional-imaging) is an effective method for evaluating the pulmonary function of postoperative lung according to the lung volume measurement.