Acute disseminated encephalomyelitis (ADEM) is an inflammation of the spinal cord and brain. Diagnosis of ADEM, due to its rare occurrence and lack of definite laboratory indices, is difficult and is never totally certain. The clinical criterion required for the diagnosis is presence of acute symptoms from the brain and/or spine with fever, occurring after viral or bacterial infection, vaccination or serum administration. Differentiation between ADEM and acute multiple sclerosis in children is difficult, and diagnosis of ADEM may only be confirmed after years of observation, especially as multiple sclerosis is more common than ADEM. The most useful tool in differentiation between the two diseases is MRI. The aim of the study was to present two cases of ADEM with unknown aetiology after aseptic meningitis in children.