In this article, data about psychoneurological and neurophysiological examination of cognitive functions in children with cerebellum neoplasms are presented. For the first time the phenomenon of functional cognitive aggravation of children in early postoperative period is described. On the base of three-dimensional EEG was established that in case of cerebellum hemisphere and vermis affected, there is no difference in the frequency of the localization of biopotential dipoles of 0,5-35 Hz in the thalamus; when the vermis is affected, brainstem and limbic structures of brain are implied; the cerebellum hemispheres injuries are associated with the symptomatology belong to cortical- basal front structures.