Pyogenic intraventricular empyema (PIE) is a potentially fatal CNS infection. However, it is sometimes difficult to diagnose PIE on the basis of clinical and conventional MRI findings. Diffusion-weighted imaging (DWI) has been accepted as a useful MR sequence for the diagnosis of various intracranial infections. The purpose of this study was to determine the DWI characteristics of PIE and the role of DWI in the diagnosis of PIE.