Yes / Involving patients and the public in all stages of research has been the focus of the SHARED study. Patient and public involvement (PPI) is an important strategic priority for the Department of Health and funders such as the National Institute for Health Research. The aim of this paper is to describe the benefits, challenges and costs involved in setting up the research study with lay members as part of the research team. The study focused on developing service user-led recommendations for people with memory loss and their carers, on discharge from acute hospital to the community. Methods: This began with a discussion of an initial research idea with a lay group of carers and people living with dementia. Once funded, approval was sought from the Research Ethics Committee and NHS Trusts to conduct the research including the active involvement of lay co-researchers. Finally, to recruit, train and pay lay co-researchers in their role. Results: The benefits of PPI have included developing ideas which are important to people living with memory loss; support for PPI received from the funders and research ethics committee, high levels of interest from volunteer groups, and lasting enthusiasm from many of the co-researchers. Organisational challenges were met in the requirement for research passports and with payment methods for the co-researchers. Training was beneficial but incurred extra costs for repeated training days. Discussion: Overall the benefits outweighed the challenges which were overcome to varying degrees. The lay co-researchers gained membership of a study group and a beneficial partnership developed with the third sector. The biggest challenge was in overcoming the differences in approach to lay co-researchers between NHS Trusts. Organisational culture has been slow to incorporate PPI and this has not yet been fully addressed. It has the potential to delay the start of projects, affect recruitment time, incur extra research costs and disadvantage PPI.