Functional reorganization of the motor system following brain damage has been studied extensively in stroke patients, in which not only the cerebrum but also the cerebellum (CbII) undergoes substantial reorganization. However, the role of CbII in motor functional reorganization in brain tumor patients remains poorly investigated. Because brain damages in brain tumor patients occur much more slowly than in stroke patients, the neural mechanisms for motor functional reorganization might differ between these two disease conditions. This functional magnetic resonance imaging (fMRI) study investigated whether CbII constitutes the neural substrates for motor functional reorganization in eighteen supratentorial brain tumor patients who exhibited no clinical signs of paresis. The patients and normal volunteers underwent a unilateral hand movement task. In the patients, the locus of primary sensory motor (SM1) activation during contralesional hand movement was significantly displaced by the tumor, suggesting functional compromise and/or reorganization in the central sulcus region. In addition, their contralesional CbII activation during contralesional hand movement was substantially increased as compared to normal controls. The finding represents the first conclusive evidence that CbII is involved in the motor-related functional reorganization in patients with brain tumor. (C) 2016 Elsevier Ireland Ltd. All rights reserved.