OBJECTIVES: F18-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT), which allows differentiation between malignant and benign lesions based on difference in tissue glucose metabolism, has become increasingly important in lung cancer diagnosis. This study examined the clinical value of FDG-PET/CT in a large number of patients with non-small cell lung cancer (NSCLC) after potentially curative surgery. METHODS: Four hundred and ninety FDG-PET/CT of 241 patients (143 males and 98 females; age range 38-87 years; mean 68.0 years) between May 2006 and February 2008 were retrospectively evaluated. All the 241 patients had undergone potentially curative surgery for NSCLC >6 months before FDG-PET/CT and their pathologic stages were stage I and II according to the tumor-node-metastasis (TNM) classification. A final diagnosis of recurrence was confirmed by histologic or cytologic examination of the disease or by clinical and radiologic follow-up image analysis. Confirmation of recurrence-free status was based on a clinical and radiologic image analysis follow-up period of at least 12 months with no evidence of active malignancy. The diagnostic performance of FDG-PET/CT was evaluated. Details of false results and incidental detection of diseases other than recurrent lung cancer by FDG-PET/CT was also analyzed. RESULTS: Recurrences were confirmed in 35 (15%) patients, and 206 patients (85%) had no evidence of recurrence. FDG-PET/CT correctly diagnosed recurrence in 34 of 35 patients and provided true negative findings in 198 of 206 patients who had no evidence of recurrence (sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of 97%, 96%, 96%, 81%, and 99%, respectively), indicating a high diagnostic performance. However, one patient had false negative studies and eight patients had false positive studies; misdiagnosis was more frequently in intrathoracic sites associated with postoperative changes. Malignancies other than recurrence were detected in nine of all 241 patients (4%) including five second primary lung cancers. CONCLUSIONS: The present study demonstrated the high diagnostic performance of FDG-PET/CT in detecting recurrences in a large group of patients with NSCLC after potentially curative surgery. FDG-PET/CT is useful not only for diagnosis of recurrence but also for detection of other diseases.