Much has been written about the importance of involving service users in the research process. Far less is available about the experience of involvement from the perspective of service users themselves. The present paper is a joint account by service users and researchers of a service users' advisory group set up to support and advise a project to evaluate diabetes services in Bradford, UK. The establishment of a separate advisory group for service users is, to our knowledge, an innovative approach to lay involvement within mainstream National Health Service (NHS)-based research. Factors that contributed to the group's success included personal contact, continuity of membership and integration into the management structure of the project. Also valued were the confidence in numbers which membership of the group gave, and the opportunity to meet and discuss issues away from the formal and somewhat intimidating atmosphere of the project's steering group. Aside from the personal value to participants and any impact on the quality of research outcomes, wider benefits included the ability to share knowledge with others and gain greater intercultural understanding.