We studied five patients with mediastinal lymph node enlargement suggestive of malignant lymphoma, lung cancer, or sarcoidosis. Integrated [(18)F]fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) was performed on all patients. Sarcoidosis can be a pitfall in PET/CT imaging, which may lead to false-positive results of malignancy. Increased FDG uptake in mediastinal lymph nodes is often comparable with malignant lymphoma or lymph node metastases. Histological confirmation of the lesions should be mandatory, except for patients in whom sarcoidosis can be accurately confirmed by other diagnostic methods.