The prevalence and severity of pediatric obesity have dramatically increased since the late 1980s, raising concerns about a subsequent increase in cardiovascular outcomes. Strong evidence, particularly from autopsy studies, supports the concept that precursors of adult cardiovascular disease (CVD) begin in childhood, and that pediatric obesity has an important influence on overall CVD risk. Lifestyle patterns also begin early and impact CVD risk. In addition, obesity and other CVD risk factors tend to persist over time. However, whether childhood obesity causes adult CVD directly, or does so by persisting as adult obesity, or both, is less clear. Regardless, sufficient data exist to warrant early implementation of both obesity prevention and treatment in youth and adults. In this Review, we examine the evidence supporting the impact of childhood obesity on adult obesity, surrogate markers of CVD, components of the metabolic syndrome, and the development of CVD. We also evaluate how obesity treatment strategies can improve risk factors and, ultimately, adverse clinical outcomes.