Over the past years, positron emission tomography (PET) with fluoro-2-deoxy-D-glucose (FDG) has emerged as an important imaging modality. In the thorax, FDG-PET has been shown to differentiate benign from malignant pulmonary lesions and stage lung cancer. Preliminary studies have shown its usefulness in assessing tumor recurrence, and assisting in radiotherapy planning. FDG-PET is often more accurate than conventional imaging studies, and has been proven to be cost-effective in evaluating lung cancer patients. This review will discuss the current applications of FDG-PET as compared with conventional imaging in diagnosing, staging, and following patients with lung cancer.