Lymphomatoid granulomatosis (LG) is an uncommon disease now regarded by most authors as an unusual form of lymphoma with the ability to affect any bodily system. The disease and its complications may result in a spectrum of radiological appearances. A case illustrating how cerebral lesions may mimic demyelinating plaque, neoplasm or infection and how pulmonary lesions may lead to pneumopericardium is presented. The difficulty in establishing a definitive diagnosis, due to the non-specificity of symptoms, pathological investigations and radiological appearances of the disease, is emphasized. Clinicians must therefore consider LG in their differential diagnoses, as delayed treatment may affect prognosis.