This article explores the institutional factors shaping the impacts of public participation on the processes and outcomes of science-based policy-making. The article draws on the example of UK food safety regulation, which has been at the forefront of attempts in the UK to actively engage the public in decision-making since the creation of the UK Food Standards Agency in 2000. Four diverse examples of participative processes dating from the late 1990s to the present day are explored in order to chart how conceptions of participative reforms have changed over time and to analyse the impacts of those reforms on policy processes and outcomes. The article shows how the impact of participative practices on policy-making has been dependent on their ability to adapt to, and reinforce, rather than challenge, deeply entrenched policy-making norms, practices and cultures. Where participative processes have posed challenges, they have tended to be conceived and organised in ways that have minimised threats to policy practice. The analysis shows how, over time, the conceptions and practices of participation are dynamically shaped by active processes of domestication', whereby practices are institutionally selected' and adapted' to fit with entrenched policy needs, demands and expectations.