A 66-year-old man was found to have a nodular shadow, 35 × 30mm, in the right middle lung field on a chest x-ray film during treatment for chronic obstructive pulmonary dinease. Fiberoptic bronchoscopy revealed a mass obstructing the right B6 with irregular mucosa extending to the right lower bronchus, and another small mass was detected on the left B3. Endobronchial biopsies of both lesions showed squamous cell carcinoma. The left lung tumor was not visible on chest x-ray films. Spirogram results were : FVC, 2.61 L; percent predicted FVC, 78.4 %; FEV1.0, 1.56 L; FEV1.0/FVC ratio, 59.8 %. Predicted postoperative FVC of 1.4-1.5 L and FEV1.0 of 0.8-9L after resection of the right lower lobe and left S1+2+S3 were determined by preoperative spirometry and quantitative 99mTc-MAA perfusion scan.Both tumors were resected, first by right lower sleeve lobectomy, with preservation of the middle lobe, for squamus cell carcinoma in the right S6 with superficial infiltration extending to the lower lobe bronchus. Two months later left S1+2 +S3 segmentectomy was performed for the early hilar squamous cell carcinoma of the left B3. Histological exmaination showed that the B3 lesion was composed, for the most part, of carcinoma in situ. Regional lymph nodes obtained during both operations were free of metastasis. Our diagnosis was multiple primary lung cancers according to the criteria suggested by Martini et al.The paient underwent curative resection without postoperative respiratory embarrassment. Spirogram and 99mTc-MAA perfusion and 81mKr ventilation lung scans were performed serially after operation. Spirometric results improved with time and have been stable since about six months after operation. Although a discrepancy was found between the distribution of perfusion and ventilation in the early postoperative period, it diminished several months after operation. The patient is at present disease-free with a adequate pulmonary function.