The transition from childhood to adulthood through adolescence has been clearly identified as a time of great physical, psychological, emotional, social, and sexual change. Clinical care is currently divided into adult or pediatric care; adolescent patients require specific expertise that most clinical practices do not have. When illness coincides with the adolescent transition, the health system is severely challenged. Health systems historically have varied widely in the age they choose for allocating an individual to the adult model of health care. Tumors of the CNS complicate the difficult adjustments required in adolescents and young adults by virtue of their morbidity, complex treatment, and prognosis. Some brain tumors are unique to children, some occur predominantly in adults, and others peak in adolescence. Delays in the diagnosis of brain tumors can occur at any age but are particularly common in adolescence because of difficulties of accessing health systems, the difficulties of discriminating pathologic from typical adolescent behavioral characteristics, and changing endocrine function. Coming to terms with the cancer diagnosis; coping personally, socially, and financially with cancer treatments; accepting the risk of a shortened life span; confronting acquired disability; and coping with complex rehabilitation and adjusted plans for life are challenges for which there are no established specialist health models. This article will discuss the changing brain tumor profile of children, adolescents, and adults, with a focus on our limited understanding of the adolescent/young adult transition period.