Objective: Aim of the study was to assess the duration of preoperative external ventricular drain (EVD) as a predictor for permanent cerebrospinal fluid (CSF) diversion in pediatric posterior fossa tumors. Methods: The study was conducted in the Department of Pediatric Neurosurgery, National Neuroscience Institute, King Fahad Medical City, Riyadh, Saudi Arabia from January 2010 to December 2013. The data were collected retrospectively. The patients who had emergency insertion of external ventricular drain (EVD) due to hydrocephalus before the definitive posterior fossa tumor surgery were included in the study. Results: The preoperative emergency insertion of EVD was done in 38 patients with pediatric posterior fossa tumors. The patients were divided into two groups. Group A consists of those patients who had duration of preoperative EVD equal or less than 7 days. Group B includes those patients who had duration of preoperative EVD more than 7 days. Group A has 16 patients while Group B has 22 patients. The predominant clinical feature was symptoms and signs of raised intracranial pressure (ICP) only. Infection related to EVD was seen in seven patients. Ventriculoperitoneal (VP) shunt was required in 31.25% of Group A patients and 18.18% of Group B patients (p value = 0.35). Overall shunt rate was 23.68%. Conclusion: There are well known number of factors that can determine the need of permanent CSF diversion in patients with posterior fossa tumors. However, there is no effect of preoperative duration of EVD in determining the requirement of postoperative VP shunt.