A case of Erdheim-Chester disorder, a rare non-Langerhans' cell histiocytosis, was referred for restaging by F-18 FDG PET/CT more than 10 years after initial diagnosis. The patient presented diabetes insipidus, hypergondotropic hypogonadism, and osteosclerotic lesions. Previous bone scintigraphy documented pathognomonic long bones' involvement. Chronic steroid and hormone replacement therapy was administered, and the patient was asymptomatic. F-18 FDG PET/CT was useful for disease restaging at cardiac and soft tissues level.