Background: Cigarette and alcohol use are common among youth. We examined sources of cigarettes and alcohol among youth who were current cigarette and alcohol users. Methods: We analyzed nationally representative data from the 2009 and 2011 national Youth Risk Behavior Surveys--biennial, school-based surveys of high school students in the United States. Students completed anonymous, self-administered questionnaires. Overall response rates were 71% for both years. Results: Among the 17.3% of current cigarette users <18?years, 27.3% usually gave someone else money to buy their cigarettes and 27.7% usually borrowed (bummed) them. Fewer (14.1%) usually bought their own cigarettes in a store. Among the 40.3% of current alcohol users, 24.3% usually gave someone else money to buy it and 41.2% usually had someone give it to them. A few (4.5%) usually bought their own alcohol in a store. Age and intensity of use were positively associated with students buying their own cigarettes or alcohol, but negatively associated with students borrowing or having someone else give it to them. Conclusions: Because social and commercial sources of cigarettes and alcohol are common, multiple strategies are needed to reduce the ability for youth to obtain them and reduce their desire for them.