Patient and public involvement (PPI) in research has expanded nationally and internationally over the last decade, and recently there has been significant attention given to understanding its impact on research. Less attention has been given to the impact of PPI on the people involved, yet it has been shown that the success of PPI in research can be reliant on the processes of engagement between these individuals and communities. This paper therefore critically explores the impact of PPI on service users, researchers and communities involved in health and social care research.