This research examined whether intentions aligned with moral norms better predict behaviour compared with intentions aligned with attitudes. Six data sets predicting behaviours in the health domain (smoking, driving over speed limit, applying universal precautions, exercising) were analysed. Moderated regression analysis indicated that participants whose intentions were more aligned with their moral norm were more likely to perform behaviours compared with participants whose intentions were more aligned with their attitude. However, further analysis indicated that this moderation effect was only present when participants construed the behaviour in moral terms. The findings suggest that the theory of planned behaviour should more clearly acknowledge the importance of internalized norms and self-expectations in the development of one's motivation to adopt a given behaviour.