Autopsy studies have shown that atherosclerosis begins in adolescence in otherwise healthy individuals, and imaging techniques have shown that atherosclerosis develops earlier and is more prevalent in children with diabetes than in age-matched healthy controls. Cardiovascular disease has now overtaken diabetic nephropathy as the leading cause of premature mortality in young adults with diabetes, and the emphasis on disease prevention has accordingly shifted to a younger age group. The majority of children and adolescents with diabetes have suboptimal blood glucose control, and this contributes to accelerated arterial disease in this age group. Other conventional risk factors for coronary heart disease also need to be considered and treated aggressively. Effective early prevention of cardiovascular disease will involve lifestyle modification and full implementation of existing treatment guidelines, and large-scale prospective studies will be needed to establish the risks and benefits of early pharmacological intervention in children and adolescents.