Objective To investigate the effect of endoscopic third ventriculostomy(ETV)on congenital obstruc? tive hydrocephalus in pediatric patients. Methods We prospectively evaluated the postoperative neurodevelopmental out? comes in 33 children with congenital obstructive hydrocephalus who underwent endoscopic third ventriculostomy at differ? ent ages from June 2011 to Jan 2014. According to their ages at the time of surgery, we categorized them into two groups: ETV≤6 months of live group(n=17)and ETV>6 months of live group(n=16). We assessed postoperative neurodevelop? mental outcomes using Gesell developmental diagnosis schedule which included gross motor, fine motor, adaptive, linguis? tic and personal-social functions. Results There was statistical significance in neurodevelopmental outcomes between two groups(P ﹤0.05). Patients in ETV>6 months of live group presented better outcome scores in all assessed domains than those in ETV≤6 months of live group (23.00±3.62 vs. 48.81±6.81; 25.94±3.07 vs.55.56±8.40; 15.00±3.06 vs. 40.94±6.69; 20.00±3.06 vs. 45.81±6.81; 21.12±3.22 vs. 45.88±7.22 ). Sixteen (100%) patients in ETV≤6 months of live group had severe neurodevelopmental disability whereas only one (6.25%) patient in ETV>6 months of live group had se? vere neurodevelopmental disability. Conclusions Endoscopic third ventriculostomy on infants with obstructive hydroceph?alus before six month of ages is associated with low operative success rate and poor neurodevelopmental outcomes.