Background. Posterior fossa syndrome (PFS) is defined as the temporary and complete loss of speech after posterior fossa surgery. The goal of this study was to identify incidence and risk factors for PFS and to determine accompanying neurobehavioral and psychologic problems. Procedure. Between May 2007 and April 2009, children with brain tumors having posterior fossa surgery were evaluated neurologically and psychologically in preoperative and postoperative period. Results. PFS developed in 9 patients among 36 (25%) included in the study. Mutism continued for 120 days in one patient. Histopathological diagnosis (P = 0.05), location of the tumor (P = 0.05) and socioeconomic level of the family (P = 0.06) gave the significant results in relation with the PFS by univariate analyses. In multivariate analysis the risk of developing PFS was found 7.2 times higher in patients with medulloblastoma, 6.7 times higher in tumors located at the midline, 5.7 times higher in families with low socioecnomic level. Intelligence quotients of the patients in PFS and other group (P = 0.85) with Wechsler Intelligence Scale for Children and the results of the Denver II Developmental Screening Test were not significant statistically (P = 0.5). Conclusion. The diagnosis of medulloblastoma, midline location of the tumor and low socioeconomic level of the families are important risk factors for the development of PFS. These findings support the hypothesis that temporary ischemia and edema due to retracted and manipulated dentate nuclei and superior cerebellar pedincles may be the cause of mutism. Pediatr Blood Cancer 2011;56:206-210. (C) 2010 Wiley-Liss, Inc.