Neurological complications are frequent in the course of malignant hematological diseases. Five cases occurring in children are reported here: 4 presented with acute lymphoblastic leukemia and 1 with lymphoma. The clinical pattern was remarkably acute, with fever, seizures and a neurological deficit. Brain CT scan showed a limited hypodensity sometimes with a contrast uptake in the involved area in the first days or weeks. Seroconversion for measles virus occurred in 3 cases, associated with the presence of helix-like bodies in the cerebrospinal fluid and/or cerebral tissue. These case reports are discussed with respect to the neurological complications already reported in patients with hematologic malignancies. The hypothesis of measles-virus related encephalitis seems likely.