The patient was a 45-year-old woman with a history of a right lower lobectomy for lung adenocarcinoma two years earlier. She complained of fever, and the computed tomography (CT) scans showed ground glass opacification in the right upper lobe and an infiltrative shadow in the right middle lobe; we therefore suspected pneumonia. Although her symptom improved within several days and the infiltrative shadow in the right middle lobe diminished, the ground glass opacification in the right upper lobe increased. Since bronchoscopy did not lead to a diagnosis, we performed a CT-guided percutaneous needle biopsy. Pathological findings showed coagulative necrosis and hemorrhage, thus we diagnosed pulmonary infarction. Retrospective review of preoperative CT scans showed that the A² pulmonary artery branched from the A⁶ pulmonary artery, and the postoperative CT scans revealed that A² was no longer discernible. This indicated that A² had been resected during the right lower lobectomy. Since the pulmonary infarction occurred in the S² segment of the right upper lobe, the resection of A² was presumably related to the pulmonary infarction. We suggest that pulmonary infarction should be considered as a differential diagnosis when shadows appear after pulmonary surgery.