Health-promoting messages can be framed in terms of the gains that are associated with healthy behaviour (gain frame) or the losses that are associated with unhealthy behaviour (loss frame). In the present research, we examined the role of positive and negative affect in the persuasive effects of gain- and loss-framed health-promoting information. Experiment 1 (N = 98) showed that gain-framed information resulted in higher levels of information acceptance than loss-framed information and that this effect was mediated by positive affect. The results of Experiment 2 (N = 129) showed that gain-framed information resulted in higher levels of information acceptance and attitude, an effect that was again mediated by positive affect. In addition, loss-framed information resulted in more negative affect than gain-framed information and negative affect increased participants' intention to engage in the healthy behaviour. These results suggest that affect may be of great importance in the persuasion process and may be particularly helpful to explain the underlying mechanisms of message framing effects. The findings also suggest that gain- and loss-framed messages offer distinct pathways to persuasion. Copyright © 2009 John Wiley & Sons, Ltd.