Dandy-Walker syndrome (SDW) is a rare brain malformation that can be isolated or associated with other malformations. The diagnosis can be established in antenatal or postnatal, and the prognosis is related to the importance of the hydrocephalus and to frequent malformation associated.We propose, through these 3 observations, the contribution of obstetrical ultrasound and fetal MRI in theprenatal diagnosis of Dandy Walker syndrome, and the role of different methods in symptomatic treatment.