Acute cerebellitis is an inflammatory process involving the cerebellum. We report the clinical, CT and MRI features of four cases and a review of the literature. Bilateral diffuse hemispheric abnormalities represent the most common imaging presentations. Our observations demonstrate the various imaging appearances of acute cerebellitis. Simultaneous involvement of both hemispheres and the vermis has not been reported previously. The development of cerebellar atrophy following an initial normal MR imaging examination is also a new finding. In atypical clinical presentation, MR imaging can lead to the diagnosis. MR imaging findings have, however, no prognostic value.