Lung cancer has become a leading cause of cancer death in Korea. Accurate staging of non-small cell lung cancer (NSCLC) is essential to the ability to offer a patient the most effective available treatment and the best estimate of prognosis. PET with F-18 fluorodeoxyglucose (FDG) is indicated for the nodal staging of NSCLC and detection of distant metastases. Use of PET for mediastinal staging should not be relied on as a sole staging modality, and positive findings should be confirmed by mediastinoscopy. FDG PET avoids futile surgery by a more accurate selection of patients, especially by the detection of unexpected distant metastases.