Background: To improve postoperative outcomes associated with interstitial pneumonia (IP) in patients with lung c ancer, t he m anagement of t he p ostoperative a cute e xacerbation of I P (PAEIP) was investigated. Methods: Patients with primary lung cancer were considered to be at risk for PAEIP (possible PAEIP) based on a preoperative evaluation. The early phase of this study was from January 2001 to December 2008, and the late phase was from January 2009 to December 2014. In the early phase, chest computed tomography (CT) was performed for patients for whom PAEIP was suspected based on their symptoms, whereas in the late p hase, chest CT w as r outinely p erformed w ithin a few days p ostoperatively. The n umbers o f possible PAEIP cases, actual PAEIP cases, and deaths within 90 days due to PAEIP were compared between both phases. Results: In the early and late phases, surgery was performed in 712 and 617 patients, 31 and 72 possible PAEIP cases were observed, nine and 12 actual PAEIP cases occurred, and the mean interval from the detection of PAEIP to starting treatment was 7.3±2.3 and 5.0±1.8 days, respectively. Five patients died in the early phase, and one patient died in the late phase. Significantly fewer PAEIP-related deaths were observed in the late phase (p＜0.05). Conclusion: Identifying patients at risk for PAEIP by routine postoperative CT examinations led to the early diagnosis and treatment of PAEIP, resulting in the reduction of PAEIP-related mortality.