Dyke-Davidoff-Masson syndrome (DDMS) was first described in 1933 and characterized by cerebral hemiatrophy. The etiology of this syndrome may be classified as congenital or primary and acquired or secondary. Diagnosis can be made by computerized tomography (CT) or magnetic resonance imaging (MRI). A one-year-old boy with congenital type of DDMS in an identical twin is described in this paper as the first case documented.