Whole-body PET scanning was performed using 18F-fluorodeoxyglucose (FDG) in two patients with hilar lymphadenopathy in whom the clinical differential diagnosis was between sarcoidosis and lymphoma. Both patients were later proven to have sarcoidosis. Uptake of 18FDG was seen in both intra- and extrathoracic lesions as well as in associated erythema nodosum. One patient underwent a repeat scan after steroid therapy where a marked decrease in hilar uptake was seen. Fluorine-18-fluorodeoxyglucose uptake is observed in lymph nodes with sarcoid involvement. Further investigation is necessary to assess if quantitative differences exist between sarcoid and malignant lymphadenopathy.