PurposeAlthough rates of adolescent cigarette use have remained constant or decreased, rates of marijuana and e-cigarette use are rising. Knowledge and perceptions of risks and benefits of tobacco products impact adolescents' decisions to use these products. However, little is known regarding adolescents' knowledge and perceptions of risks of e-cigarettes and marijuana nor how these perceptions are formed. This study uses qualitative techniques to assess and compare adolescents' perceptions of the risks and benefits of cigarettes, e-cigarettes, and marijuana. MethodsTwenty-four adolescents (nine females and 15 males) from Northern California participated in six small-group discussions. Adolescents were asked what good or bad things might happen from using these products. To assess how perceptions and knowledge of risks and benefits were formed, participants were asked where and from whom they had learned about these products. ResultsAdolescents described negative consequences of cigarette use but were much less sure regarding risks of marijuana and e-cigarette use. Conversely, they described few benefits of cigarettes but described a number of benefits of e-cigarette and marijuana use. Adolescents described learning about these products from the media, from family and friends, and from the school environment. ConclusionsAdolescents have learned from multiple sources about risks of using cigarettes, but they receive much less and often incorrect information regarding marijuana and e-cigarettes, likely resulting in their positive and often ambivalent perceptions of marijuana and e-cigarettes.