PURPOSE: The outcome of endoscopic third ventriculostomy (ETV) is worse in children younger than 2 years old and especially in infants, and controversies still exist whether ETV might be superior to shunt placement in this age group. We retrospectively analyzed the data of 23 patients younger than 6 months of age treated with ETV and assessed its feasibility as a first choice of treatment for hydrocephalus. METHODS: Between 1994 and 2008 in our clinic, 23 patients younger than 6 months having presented with obstructive hydrocephalus were treated endoscopically. The etiology of hydrocephalus was congenital aqueduct stenosis in 11 patients, posthemorrhagic obstruction in six patients, myelomeningocele in two patients, postmeningitis in two patients, Chiari I malformation in one patients, and Dandy walker variant in one patient. ETV was considered successful when no shunt operation was needed in the patient. RESULTS: ETV was successful in eight patients with regression of intracranial hypertension. In the remaining 15 patients, ventriculoperitoneal shunt implantation was necessary. Total success rate in our group of patients was 34.8%. In patients younger than 3 months of age (n=12), success rate was 25.0%. In patients from 3 to 6 months of age (n=11), success rate was 45.5%. Complication included intraventricular hemorrhage in one patient, meningitis and cerebrospinal fluid leak in one patient, and meningitis in one patient. CONCLUSIONS: Based on our experience, ETV could be the first method of choice for hydrocephalus in children younger than 6 months of age, especially in patients older than 3 months of age.