Due to developments in diagnostics and therapeutic methods, around two-thirds of the children diagnosed with cancer are cured and reach adulthood. More attention has been drawn to the adverse effects of cancer treatments including those on bone metabolism. Potentially harmful components of cancer therapies with regard to bone development are, e.g., corticosteroids, radiotherapy, and high doses of antimetabolites, such as methotrexate. In long-term survivors of childhood acute lymphoblastic leukemia and intracranial tumors, a history of cranial radiation has been associated with reduced bone mass. More controversy exists about the development of bone mass in long-term survivors of childhood cancer when cranial radiation has not been administered. Both normal as well as decreased bone mass and mineral density has been observed in this group of childhood cancer survivors. Long-term longitudinal data on bone mass development are required to further elucidate this question.