Multiple sclerosis (MS) and acute disseminated encephalomyelitis (ADEM) are demyelinating inflammatory diseases, considered to have a striking pathophysiological resemblance. However, due to the differences in both clinical course and clinical approaches, it is important to differentiate between the two conditions, to plan further investigations and therapy protocols. These diseases have similar but also distinct clinical, radiological and cerebrospinal fluid (CSF) findings. ADEM is typically a monophasic disease of children. MS occurs generally in adult age, but uncommonly may develop in childhood with variable features. Our case is a 14 year-old-girl, presented with a three-month history of left hemiparesis, followed by right hemiparesis, cerebellar signs, myelitis and cortical visual disturbances. Based on the clinical follow-up, MR and CSF findings, our patient was diagnosed with relapsing tumefactive multiple sclerosis. Steroid treatment was not significantly effective, however the patient has benefited from plasmapheresis clinically and radiologically. Our patient is still being followed under the disease modifying therapy without any relapse.