IntroductionIn recent years, vaping prevention campaigns have proliferated in response to a surge of e-cigarette use among adolescents in the USA. To date, the research literature has provided minimal guidance as to what vaping prevention message elements have the greatest potential for discouraging vaping, are ineffective or have unintended negative effects. The purpose of the current study was to identify and test a large set of vaping prevention ads used by federal, state, local and non-governmental agencies, examining how objectively coded message elements of vaping prevention messages might affect youth.MethodsA convenience sample of adolescents (N=1501) completed an online survey with each participant rating seven randomly selected vaping prevention ads from a pool of 220 ads on perceived message effectiveness (PME) and vaping appeal. Ads were coded on 37 objective elements in three message categories: themes, imagery and other features. Analyses examined how objective elements predicted PME.ResultsAddiction, chemicals, negative health symptoms and effects, and cigarette comparison themes were associated with higher PME, as were graphic images and warning symbols. Industry targeting, environmental impact, flavour themes, images of food and people’s faces were associated with lower PME, as were hashtags, statistics and first-person language or the word ‘teen’. Most elements were not associated with appeal, but ads with a flavour theme were associated with increased vaping appeal.ConclusionPromising vaping prevention messages focus on the adverse consequences of vaping, use negative imagery and avoid speaking for teens using their vernacular or perspective.