Positron emission tomography imaging is useful for the characterization of the solitary pulmonary nodule and mediastinal staging. Potential future applications include extrathoracic staging to help to determine the ideal site for possible tissue diagnosis, to guide treatment plans, and to monitor the response to therapy and recurrence. Positron emission tomography may also predict prognosis. This review discusses the uses of positron emission tomography, the current literature, and the clinical guidelines for positron emission tomography imaging.