What people eat influences their susceptibility to disease, yet many consumers within the Western World are consuming inappropriate diets. One approach to facilitating the consumption of a healthy diet has been the development of so-called "Functional Foods" (foods that provide a health benefit beyond the traditional nutrients they contain). The ultimate aim of the thesis was to model current psychological predictors of intention to consume functional foods. A mixed method approach was utilised. Qualitative (one-to-one interviews) and quantitative (questionnaire) exploratory studies were used to inform a larger qualitative study (focus groups). Emergent key information was then used to inform a large-scale questionnaire and structural equation modelling was used to identify the predictors of intention. The interview study highlighted the important issues surrounding functional foods. The small questionnaire determined the further research on a) conditions important to consumers and b) conditions that varied along a perceived genetic scale (Alzheimer's disease, Cardio Vascular Disease and Stress). The focus groups highlighted four design rules for the successful development of functional food ('inversion', `subterfuge', `inclusiveness' and `authenticity') and three key segments of the population ('pro-science', `conditionalists', and `negatives'). The final study modelled the three health conditions (Alzheimer's disease, Cardio Vascular Disease and Stress) and three preventative health behaviours (eating functional food, a healthy diet or doing more exercise). Multi-dimensional Health Locus of Control and perceived hazard characteristics were modelled as predictors of risk perception. The main predictors of risk perception differed significantly by health condition. Intentions for the three preventative health behaviours were modelled using a Theory of Planned Behaviour framework. Good predictive utility was demonstrated, which was further improved by expansion of the model. Output from the research could be used to inform both psychological theory and the design of future communication initiatives. Findings are discussed with respect to practical and methodological implications and directions for future research.