Pathologic processes within the cerebellopontine angle (CPA) may present because of mass effect on local structures or on the pons or cerebellum. MR imaging is superior to CT for evaluation of the complete extent of a CPA mass and for characterization of its likely nature. MR is also superior to CT for the detection of leptomeningeal processes. Arriving at a short list of differential diagnoses requires a methodical approach, keeping in mind the location, signal, diffusion, and enhancement characteristics of the lesions. Advanced MR imaging techniques, such as magnetic resonance spectroscopy, are not usually needed routinely but may aid in the differential diagnosis when presented with atypical masses.