Accurate staging is important in small-cell lung cancer (SCLC). Patients with limited stage may benefit from chemoradiation, whereas those with extensive stage conventionally receive chemotherapy. Prophylactic cranial irradiation may benefit those attaining complete remission (CR). 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) enhances accuracy of staging in non-SCLC. Its role in SCLC remains unclear. We reviewed 36 consecutive SCLC patients who underwent 47 PET studies between December 1996 and January 2001, for either staging (n = 11), restaging after therapy (n = 21), or both (n = 4). Conventional imaging was also performed. Of 15 patients who had PET for staging, 5 (33%) were upstaged from limited to extensive disease and treated without thoracic radiotherapy. Twenty-five patients underwent 32 restaging PET scans, of which 20 (63%) were discordant with conventional imaging. In 8 cases PET showed more extensive disease than conventional imaging, and in 12 cases PET-apparent disease appeared less extensive. In 13 patients, 14 untreated discordant lesions were evaluable; PET was confirmed accurate in 11 (79%) sites by last follow-up. Restaging PET influenced management in 13 cases (52%). PET-CR conferred longer median time to progression (13.7 months) than no CR (9.7 months). FDG-PET for SCLC was often discordant with conventional assessment and frequently influenced management.