Subacute Sclerosing Panencephalitis (SSPE) is a progressive neurological disorder of childhood and early adolescence, which is presented with psychological symptoms such as cognitive difficulties and neurological symptoms. We report a case, an 11-year-old boy developing SSPE one year after diagnosis of Attention deficit hyperactivity disorder (ADHD) and articulation disorder. A 10-year-old boy, one of a twin was presented clinic with learning difficulties, attention problems and hyperactivity. Mental status examination revealed short attention span, motor hyperactivity, difficulties in writing and reading and minor articulation problems. Psychometric test, WISC-R demonstrated verbal skore: 76, performance skore:81, total score:76. In Bender Gestalt, was found in 5% percentile. Low dose methylphenidate treatment was started and risperidone was added for behavioral problems. Educational and speech therapy was planned for learning disabilities and articulation problems. Attention and behavioral symptoms were improved in one-year follow up. During the clinical course, when the child was 10 year under low dose stimulant and antipsychotic treatment, he began to fail academically, he lost some language and organization, planning skills, he developed cognitive deficiencies including memory deficits, movement disorder, myoclonic jerks. Neurological consultation was revealed typical EEG and cerebrospinal şuid findings. In this case report we point that neurodegenerative disorders in childhood might present with ADHD, especially with cognitive impairment before the clinic is overt. Whether the use of stimulant treatment has an effect on the progress of cognitive component of the disorder during the disease course, more cases are needed to investigate.