© 2013 Springer Science+Business Media New York. All rights reserved. The association of hydrocephalus and the Chiari malformations has been described from the time of Hans Chiari's initial report in 1891. Whether hydrocephalus is the cause of or the result of hindbrain herniation remains a subject of long-standing controversy, but recent advances in vascular and volumetric imaging may eventually provide definitive information to settle the debate. Though there is a wide range of hindbrain herniations that fall under the Chiari rubric, most authors would agree that coexisting hydrocephalus should be managed with CSF diversion first, either by shunting or endoscopic ventriculostomy, before consideration is given to posterior fossa decompression. It is crucial to keep in mind that pseudotumor cerebri may also present with symptoms that mimic those seen in Chiari malformation, making it critical that the neurosurgeon strive to differentiate these two groups prior to surgical intervention for optimal outcome.