Background There is increased interest from researchers in evaluating public involvement by service users in health and social care research, with debate about feasibility of doing this. Discussion is led by researchers.

Objective To describe service users' views about whether evaluating impact of public involvement in research is feasible and helpful.

Method 19 patients or carers were interviewed. All were members of the SUCCESS service user group supporting emergency, unscheduled and trauma research. Some had regular involvement in research studies about prehospital emergency care and chronic conditions management to reduce people's risk of using unscheduled services.

Results Service users found it difficult to identify their impact on research and questioned the value of thinking in those terms. Respondents said that involving people in research changed research because it changed structures, relationships and, consequently, affected the results. Involving patients and carers in research was seen as a radical approach because it challenged hierarchical relationships between academia and patients, gave value to experiential knowledge and placed this alongside clinical and academic knowledge. They also recognised the difficulty of attributing influence and measuring change over long research timescales when their contribution was describing experiences and opinions, neither of which were tangible or definitive. They also doubted they could recognise impact on studies without insider knowledge of research.

Conclusion Service users believe involvement processes are key to ensuring that patient and carer views are included when designing and undertaking research, suggesting impact on research is a consequence of effective collaborations rather than an aim in its own right. This focus on process contrasts with academic emphasis on impact and needs to be considered when discussing whether and how to measure impact.