Nineteen children were acutely dysphoric, inattentive, irritable, and sometimes mute following midline posterior fossa neoplasm resection and arteriovenous malformation hemorrhage. These symptoms represent an acute manifestation of the cerebellar cognitive affective syndrome. The authors aimed to describe the acute psychiatric changes in mood and behavior in children with posterior fossa lesions and to evaluate the relationship of posterior fossa syndrome to cerebellar cognitive affective syndrome.