Neurofibromatosis is the commonest neuroectodermal disease. It is characterized by dysplasias and/or tumors of organs and tissues derived from the embryonic ectoderm, mesoderm and endoderm, and most frequently presents with nervous system and cutaneous lesions. It can be classified as neurofibromatosis type 1 (NF-1 or von Recklinghausen disease) and neurofibromatosis type 2 (NF-2 or bilateral acoustic neurofibromatosis). In order to assess clinical presentation of the disease and diagnostic value of Magnetic Resonance Imaging (MRI), the authors retrospectively evaluated the clinical records and the cranial MR studies of 21 patients with neurofibromatosis (18 with NF-1 and 3 with NF-2). Distinctive abnormalities between the two types were found in both clinical presentation and MR studies. Clinically, NF-1 patients presented most often with blindness, while NF-2 patients were deaf and had fewer cutaneous lesions. The evaluation of MR studies showed that NF-1 patients were more likely to be affected with intracranial gliomas, predominantly of the optic pathways. Moreover, foci of prolonged T2 relaxation were frequently observed, primarily in the globus pallidus of the basal ganglia and in the dentate nucleus of the cerebellum. Some of the foci in the globi pallidi exhibited increased signal intensity on T1-weighted images as well. NF-2 patients more frequently presented with bilateral acoustic schwannomas, meningiomas and cerebral white matter foci of prolonged T2 relaxation, but they did not have dentate and basal ganglia lesions. The authors conclude that as a rule the manifestations of NF-1 and NF-2 on cranial MRI are separate and distinct; they do not overlap. MRI is an useful clinical tool for the diagnosis and the follow-up of patients with neurofibromatosis.