The overarching aim of this thesis is to gain a deeper understanding of informal carer involvement in health and social care research, from the perspective of informal carers themselves as well as from a researcher perspective.The thesis is comprised of three qualitative studies and one quantitative study. Three studies are from the perspective of informal carers, and one is from the perspective of researchers. The three qualitative studies used qualitative content analysis and discourse psychology, while the quantitative study used descriptive statistics, logistic regression and two different types of factor analysis. The data collection methods varied; in the first and the fourth studies, the data were derived from individual interviews, in the second study participants completed a questionnaire, and in the third study the data were collected from group meetings with carers.The findings showed that carer involvement in research is complex, comprising both benefits and challenges, and demands a high level of engagement from all involved, throughout the research process. The researcher must acknowledge that carers’ motivations for involvement in research vary, and the researcher should adapt their recruitment methods accordingly. It is easy to believe that becoming involved in research is an individual choice, but the findings revealed that only some carer groups choose to become involved in research. The findings also showed that the knowledge brought by carers to the research stretches far beyond their practical experiences of caring. When researchers choose to involve carers in research, their research would benefit greatly if they acknowledged the possibility that they themselves might become relationally and emotionally involved.Successful carer involvement in research therefore encompasses both a meaningful process and a meaningful result. As carers are a heterogeneous group, this places demands on a researcher’s flexibility and creativity to manage the recruitment process and involve a broad cross section of carers. If they fail in this, the research carried out and any interventions developed risk being valid for particular groups of carers and invalid in relation to other carer groups.