Tobacco use is a pervasive public health problem and the leading cause of preventable morbidity and mortality in the United States. This article reviews the epidemiology of tobacco use in youth, with a description of cigarettes, alternative tobacco product, and polytobacco use patterns among the general population and among adolescents with psychiatric and/or substance use disorders. The article also provides an update on the diagnosis and assessment of tobacco use disorder in adolescents, with a particular focus on the clinical management of tobacco use in adolescents with co-occurring disorders.