Obstructive hydrocephalus can be treated with an extracranial shunting system or, when the obstruction is between the posterior third ventricle and the fourth ventricular outflow tracts, by an endoscopic third ventriculocisternostomy (ETV). The placement of an extracranial shunting device entails significant long-term risk of infection and malfunction. This risk has led to the concept that ETV is preferable to shunting. While the long-term cognitive performance of shunted hydrocephalus patients has been extensively examined, the outcome of patients undergoing ETV has been studied only sparsely. Ten adults who had undergone ETV were entered into the study under institutional review board approval. Each patient underwent a neuropsychological testing battery that included testing within the domains of basic attention, verbal memory, visual memory, language, and executive functioning. Aggregate test scores showed a decrease in performance in the domains of memory and executive functioning when compared to normative data. The present study revealed persistent cognitive inefficiencies in memory and executive domains in patients post-ETV intervention. A larger longitudinal study considering the impact of prior shunting, presence of headaches, emotional status, and surgical complications will assist in elucidating the etiology and eventual treatment of these deficits.