OBJECTIVE The purpose of this study was to assess the usefulness of dual-energy perfusion computed tomography (CT) for predicting postoperative lung function in patients undergoing lung resection. METHODS Fifty-one patients (38 men, 13 women; mean age, 63.8 years) were prospectively enrolled and subsequently underwent dual-energy CT, perfusion scintigraphy, a pulmonary function test before surgery, and a pulmonary function test 6 months after surgery. Computed tomography was performed using dual-source CT with the dual-energy technique. Using weighted average images, each lobe was segmented and using perfusion images, the iodine value was quantitatively measured. Lobar perfusion was calculated by multiplying the volume of the lobe by the iodine value. The ratio of lobar perfusion per whole-lung perfusion was then calculated. The predicted postoperative forced expiratory volume during 1 second (post-FEV1) was calculated by multiplying the preoperative FEV1 by the fractional contribution of perfusion of the remaining lung. The agreement between the predicted post-FEV1 and the actual post-FEV1 was then evaluated. The percentage of error of the predicted post-FEV1 to that of the actual post-FEV1 was then calculated. RESULTS Using the Bland-Altman method, the limits of agreement between the actual post-FEV1 and the predicted post-FEV1 were -29.3% and 26.9% for scintigraphy and -28.9% and 17.3% for CT. The percentage of error of CT (15.4%) was comparable with that of scintigraphy (17.8%). CONCLUSIONS Dual-energy perfusion CT was more accurate than perfusion scintigraphy was for predicting postoperative lung function.