This study reviewed 66 pediatric brain tumor patients who received either proton beam craniospinal irradiation (PrCSI) (n=36) or photon beam craniospinal irradiation (PhCSI) (n=30), and found absolute lymphocyte counts and platelet counts significantly lower in the PhCSI group than in PrCSI group at every timepoint. The rate of grade 3 acute anemia was significantly lower in the PrCSI group than in in the PhCSI group.