This paper focuses on the researchers’ experiences of involvement, based on an evaluation of a pilot project supporting patient/carer involvement in research at Parkinson’s UK. Telephone interviews were conducted with researchers from eight different research projects with involvement. The researchers reported gaining new knowledge from patients and carers. They used this knowledge to change their project designs, interventions and new devices. They also gained new skills in communicating with the public. Meeting patients for the first time had a profound impact on some researchers, causing a change in their professional values. Face-to-face contact seemed particularly important to gain a sense of the ‘people behind the data’, which suggests such meetings may result in impacts beyond those typically achieved through an exchange of documents. Involvement also influenced one researcher’s choices and preferences, in terms of who to ask to take part in their study.