Background: There is not enough information available on how often hydrocephalus occurs in adult patients before and after surgery for tumors in the posterior fossa or the best way to manage it. To address this, a study was conducted to compare the effectiveness of two methods: endoscopic third ventriculostomy (ETV) and ventriculoperitoneal shunt (VPS), in reducing perioperative complications and persistent hydrocephalus in patients undergoing posterior fossa tumor surgery. Methods: A single-institution prospective study included 54 patients with 2ry obstructive hydrocephalus associated with posterior fossa tumors from November 2018 to June 2023. Different pathologies at different sites were encountered including cerebellar, cerebellopontine angle CPA, 4th ventricle, brain stem, and foramen magnum tumors. Results: A total of 54 patients; 38 ± 12.9 years, average (18 – 63) years were included in our study. Our patients were divided into two groups according to the modality of cerebrospinal fluid (CSF) diversion either ETV (23) patients or VPS (31) patients. Both ETV and VPS are valid management. Conclusion: The management of hydrocephalus due to posterior fossa tumors is still challenging. It should be handled carefully before attacking the tumors. Both ETV and VPS are valid modalities, but contemporarily, ETV by experienced hands is a safe and efficient alternative to VPS with low complication rates and better long-term outcomes. Keywords: Posterior fossa tumor, Hydrocephalus. Endoscopic third ventriculostomy, Tumor-related hydrocephalus, ventriculoperitoneal shunt.