The principal research question is, ‘What are the key domains of informed choice in cancer screening, and how best can they be measured?’ Systematic reviews were undertaken to identify the relevant qualitative and quantitative studies. Findings from the systematic reviews suggested that lay people define and conceptualise informed choice differently from researchers and policy makers. These findings were substantiated in the data from the qualitative study. The study also found that information on the disease was as important to people as information on the risks and limitations of screening. However, information may have little part to play in the choices people make. It may have more impact on outcomes such as satisfaction and anxiety. Analysis of the questionnaire data found that people had limited knowledge of the risks and consequences of screening. In addition perceived informedness was strongly predicted by attitudes rather than the knowledge of the risk and benefits. High levels of knowledge were not a predictor of the level of choice people had. The main policy reason for promoting informed choice is to enhance autonomy and to prevent people being deceived or coerced. However, this research shows that the provision of evidence-based information alone does not necessarily mean that an informed choice is made. People may not read, want, or understand the information, and, additionally, people may not be able to carry out their intended choice. For example, people may feel that they do not have the choice to refuse screening, even though they might wish to do so. Moreover there may be personal barriers, such as physical or mental health problems and language, or organisational barriers, such as the availability of the service/intervention and access.