Background
Public involvement in large-scale changes (LSC) to health services is strongly promoted – and even mandated – in several health systems. This scoping review aimed to describe the evidence about how public involvement is conceptualised and conducted in LSC, with what impact, and how different stakeholders perceived this process.

Methods
After searching eight databases, 34 publications were included. Data were extracted and charted using a standardised form. Findings from the literature were discussed with frontline stakeholders.

Results
Public involvement remains poorly defined and its aims lack clarity in LSC. Public meetings are most often used to gather public views but raise the issue of representativeness. However, evidence in the literature is scarce about which involvement methods – informative and deliberative – are appropriate for the different stages of the LSC and with what impact. In several cases, the involved public felt they had no influence on decision-making regarding LSC proposals, sometimes leading to an environment of mistrust. In those instances, the public understood the technical arguments for change and actively questioned them, opposed LSC plans and sought alternative routes to voice their views.

Conclusion
More research and consideration are needed regarding who should be involved, with what purpose and how. We argue that in practice two models of involvement, invited and uninvited participation, coexist and therefore interactions between the two should be given further consideration in LSC.