To appeal to consumers as social beings, advertisers include social settings and human images in commercial messages. Extant empirical research shows that thin models are perceived as more attractive and that the use of attractive models results in higher ad effectiveness. However, this study offers empirical evidence of ‘dark sides’ of extremely thin models, such that they harm advertising performance. The negative effects of extremely thin models stem from their influence on consumers' psychological well-being, as well as their ethical judgements of the advertisement. Respondents in this study also regard an extremely thin model as less attractive than a more average model. These results suggest that organizations should reconsider the portrayal of extremely thin models in their promotional messages and, more generally, consider consumer ethics when developing marketing communication messages.