Some rare neurological diseases affecting children have no well defined etiology and pathogenetic mechanisms. In this article diseases like Reye syndrome, Behçet disease, pediatric neurosarcoidosis, Posterior Reversible Encephalopathy Syndrome are described. Some of the main neuroradiological differential aspects are also critically considered. Reye syndrome is characterized by symmetric thalamic, white matter and basal ganglia lesions, in children with recent history of salycilates or immunosuppressive drugs intake. The most typical MRI feature of neurosarcoidosis is basilar meningeal thickening and enhancement with intraparenchymal enhancing nodules and white matter focal abnormalities. The classical distribution of lesions helps differential diagnosis with infectious meningoencephalitis. Differential diagnosis with relapsing-remitting multiple sclerosis his helped by the evidence of meningeal abnormalities. Neuro-Behçet is characterized by mesodiencephalic lesions in children with encephalopathy and coexistence of oral and genital ulcers and ocular abnormalities. PRES can be differentiated from vasculitis for the typical posterior white matter involvement and the different clinical features.