We report a case of a 26-year-old man who had sarcoidosis with involvement of central nervous system, manifested by symptoms attributable to diabetes insipidus. Laboratory tests, magnetic resonance and computed tomography images, were all partially useful and inconclusive. These investigations have been integrated with 18-Fluorine-labeled-2-deoxy-2-fluoro-D-glucose positron-emission-tomography/computed tomography (F-18 FDG PET/CT), which showed F-18 FDG uptake in the midbrain area and pituitary gland, corresponding to magnetic resonance findings, and in many bone sites, in particular iliac wings. This finding has been useful for biopsy. F-18 FDG PET/CT can demonstrate active skull-base sarcoidosis.