My PhD thesis examined the impact of children and young people's participation on policymaking in four settings: a youth forum and school council in Wales, UK, and two examples of established participation structures in the international development context including Neighbourhood Children's Parliaments in Tamil Nadu. The central aim of this study was to identify and assess the impact of children's participation in decision-making about public services at different levels of governance, with a view to testing whether devolution and the new models of governance operating in Wales since 1999 had created spaces that encompass children as ‘active participants’ in public decision-making. The two international case studies were undertaken to allow a greater understanding of what might be possible in Wales and to gain insights into how processes and outcomes may be linked. This case study explores the mechanics of undertaking comparative research on children across very different settings and illustrates how such research can make a contribution to understanding the factors that enable or inhibit children's ‘voice’ being turned into policy ‘influence’. The case study illustrates how some of the ethical and practical issues of undertaking research with children might be addressed to maximise the benefits to the children involved and safeguard their rights and interests.