Objective.  Advances in web‐based animation technologies provide new opportunities to develop graphic health communications for dissemination throughout communities. We developed imagery and text contents of brief, computer‐based programmes about heart disease risk, with both imagery and text contents guided by the common‐sense model (CSM) of self‐regulation. The imagery depicts a three‐dimensional, beating heart tailored to user‐specific information.Design.  A 2×2×4 factorial design was used to manipulate concrete imagery (imagery vs. no imagery) and conceptual information (text vs. no text) about heart disease risk in prevention‐oriented programmes and assess changes in representations and behavioural motivations from baseline to 2 days, 2 weeks, and 4 weeks post‐intervention.Methods.  Sedentary young adults (N= 80) were randomized to view one of four programmes: imagery plus text, imagery only, text only, or control. Participants completed measures of risk representations, worry, and physical activity and healthy diet intentions and behaviours at baseline, 2 days post‐intervention (except behaviours), and 2 weeks (intentions and behaviours only) and 4 weeks later.Results.  The imagery contents increased representational beliefs and mental imagery relating to heart disease, worry, and intentions at post‐intervention. Increases in sense of coherence (understanding of heart disease) and worry were sustained after 1 month. The imagery contents also increased healthy diet efforts after 2 weeks. The text contents increased beliefs about causal factors, mental images of clogged arteries, and worry at post‐intervention, and increased physical activity 2 weeks later and sense of coherence 1 month later.Conclusion.  The CSM‐based programmes induced short‐term changes in risk representations and behaviour motivation. The combination of CSM‐based text and imagery appears to be most effective in instilling risk representat