Two patients (11 and 23 months old, respectively) had successful transcatheter occlusion of congenital arterio-venous or veno-venous malformations using detachable silicone balloons. Patient 1 with a cervicofacial hemangioma had selective embolization of the feeding artery with two balloons. Patient 2, with a veno-venous malformation between a systemic vein and pulmonary vein also had selective embolization of the lesion with two balloons. Follow-up examinations confirm a successful outcome in both cases.