Objectives: To investigate cognitive and motor functioning in children treated for brain tumours. To also assess processing speed as a possible mediator in the outcomes of children treated for medulloblastoma in the posterior fossa. Design: A cross-sectional design was used. There were two groups. Children treated for medulloblastomas, and an age and gender matched non-CNS control group of children treated for Wilm's tumours. There were 14 participants in each group. Participants were aged between nine and 16 years old. Methods: Participants were assessed using measures for processing speed, attention, fine motor and visual motor co-ordination. Long-term outcomes were assessed using measures of intelligence (IQ), academic achievement, adaptive functioning, social functioning, and resilience. Results: There were significant differences between the two groups. Participants treated for medulloblastoma were significantly impaired on measures of processing speed, attention, fine motor and visual motor co-ordination. The medulloblastoma group performance was also significantly worse on measures of IQ, academic, adaptive, and social functioning. Interestingly, processing speed was found to be a significant mediator in the outcomes measured. When processing speed was co- varied, the group differences were no longer significant. Conclusion: The results of this study offer information on the impact of medulloblastoma on cognitive and motor abilities. It also offers novel information concerning the processing speed as a possible mediator in long-term outcomes of 3 children treated for medulloblastoma. This information will help with the design of interventions to target specific deficits. This will also provide additional information on the links between processing speed and outcomes. 4