In the treatment of pediatric medulloblastomas, cranial radiation therapy (CRT) may induce long-term effects including CRT-induced vascular injury and cognitive impairments. 7T Susceptibility-weighted MRI was used to characterize CRT-induced injury in the form of cerebral microbleeds (CMBs) as potential markers of cognitive deficits. The majority of CMBs were located in the frontal lobe, which develop late in the adolescent brain. CMB density was associated with deficits in working and visual memory as a function of time since CRT. This work supports a modification of future standards for defining radiation target volumes, with evidence for early intervention with cognitive rehabilitation strategies.