One of the traditional pitfalls of CT perfusion is limited coverage of the brain. However with improving multi-detector CT, larger coverage can be obtained (at the cost of increased radiation dose). The posterior fossa can be difficult to analyze due to streak artefacts and the small volume of brain. However, as demonstrated in this case, acute infarcts can also be picked up in the posterior fossa. In the setting of an apparently 'normal' CT perfusion, the brainstem and cerebellar hemispheres should be review areas.