Positron emission tomography (PET), when used with F-18 fluoro-deoxyglucose (FDG), contributes to the evaluation of patients with lung cancer. This technique of imaging detects active tumor tissue by showing increased radiopharmaceutical uptake by metabolically active cells. Thus, PET assists in the early diagnosis of pulmonary malignancies that appear only as non-specific findings on CT-scan or chest X-ray. In addition, it is helpful in staging lung cancer before and after resection, chemotherapy or radiotherapy, or their combined use. We performed 135 FDG-PET studies between July '97-April '99 and present our preliminary results with examples of the main indications for PET in lung cancer.