It is important to clarify what is meant by the term ‘service users’. We all make use of some services and service users of research are therefore a very broad group. In this chapter, we are defining service users specifically as the children, adults, students, families or identified groups who may be receiving specialized services (such as looked after children, children with identified special needs, older people), and on which much social science research focuses. However, they are rarely involved in this research, beyond their role as respondents.