Patient and public involvement activities bring 'lay participants' and their accounts of lived experiences to the centre of health service development and delivery. For individuals, these accounts can provide an important resource, offering a sense of control and an opportunity to re-frame past events. Furthermore, as involvement activities and the use of personal accounts have become more prominent, it is timely to examine the involvement process from the perspective of the 'lay participants'. Hence, the aim of this study is to explore how people become involved and how they construct the accounts of their lived experience. We analyse the stories of people with lived mental illness or caring experiences, who have become experts by experience (n = 13). We argue that becoming an expert by experience can help to re-contextualise past experiences and support the rediscovery of skills and expertise, leading experts by experience to construct both professionalised and politicised identities. The process has the potential to enforce narratives that portray illness experiences as motivators for social action and change. Additionally, we claim that the stories experts by experience share with health services and the public are not 'lay accounts' or ad hoc tales, but accounts constructed to serve specific purposes.