The report is the result of research into the impact of children's participation on development programmes and how such participation can be facilitated. The report also assesses how large international organisations with complex systems and hierarchical management structures can respond sensitively and flexibly to the challenges that will emerge when children are given a voice. It brings together the findings of a literature review of current thinking about children's participation and its evaluation with a field study undertaken in three different countries (Ecuador, India and Kenya). It is also enriched by discussion at a one-day conference in London in November 2003, which was hosted by Plan UK to review findings from the research. The report raises questions about the way that participation is understood by development agencies, arguing that the conceptualisation of children's participation by each organisation will reflect their underlying philosophies. It also focuses on the changes - both positive and negative - that children's participation may bring about, and discusses various issues relating to evaluation. Possible tools and methods are described and consideration is given to the manner in which evaluation activities are conducted. Particular emphasis is also given to ethical issues in relation to evaluation practice. The report considers the challenges for agencies in seeking to develop children's participation further, and the introduction of a participatory approach to evaluation itself.