Phase-contrast magnetic resonance imaging (PC-MRI) was at first mainly used for vascular flow quantization and many software packages were developed by MR vendors to measure blood flows in vessels. Cerebrospinal fluid (CSF) and blood flow values were calculated using the PC-MRI post-processing software. Available processing software, using automatic segmentation, makes it possible to quickly obtain a reproducible time evolution curve during the cardiac cycle. After background correction using a manually drawn area, flow parameters such as CSF stroke volume are directly calculated. PC-MRI is a valuable tool to investigate and quantify these CSF and blood flow interactions throughout the cardiac cycle. The most commonly encountered CSF disorders observed using radiological images are hydrocephalus in the brain and syringomyelia in the spine. This chapter shows how PC-MRI of CSF can help clinicians to diagnose and understand these disorders as well as how it can help neurosurgeons to guide treatment.