Objectives: Regular follow-up of patients with lung cancer treated surgically is crucial to detect local recurrence or distant metastasis of the tumor. Postoperative follow-ups are performed with thorax computed tomography (CT) and, if necessary, positron emission tomography (PET)/ CT. Sometimes, inflammatory tissue reactions due to the materials used during the surgery for hemostasis may cause the appearance of tumor recurrence in imaging modalities. In this study, we presented that oxidized regenerated cellulose (ORC) used intraoperatively may cause false tumor recurrence on PET/CT. Methods: The records of patients who had local tumor recurrence after lung cancer surgery was reviewed retrospectively. Inclusion criteria were the presence of local recurrence of cancer on PET/CT, specification of using ORC in the surgical notes, and histopathological diagnosis of the recurrence site of tumor was reported as a foreign body reaction. Data of patients were collected according to age, gender, surgery performed, adjuvant therapy status, resolution status and time ORC, and standard uptake value of 18F-fluorodeoxyglucose on PET/CT. Results: Eleven patients (1 female, 10 males) who met the criteria were included in the study. The median age was 64. Histopathological results of all patients were reported as foreign body reactions. The median detection time of PET/CT positivity after surgery was 139 days (range: 52-208 days). False tumor recurrence was resolved in 8 patients (72.7%) in their control radiological examinations and median resolution time was 334 days (range: 222-762 days). The median maximum standard uptake value of the lesions was 6.2 (1.7-11) on the PET/CT. Conclusion: ORC used intraoperatively in patients undergoing surgery for lung cancer may cause false tumor recurrence in imaging modalities in postsurgical follow-ups. When tumor recurrence is suspected in the follow-up of these patients, histopathological confirmation is necessary to prevent unnecessary operations and treatments.