Despite the widespread promotion of children's voices by activists and policy makers over the last decade, the potential for young people's knowledge to impact on adult agendas and policy arenas is by no means a certainty. This book presents critiques of participation in settings where young people are the centre of attention. The complexities and power-dynamics of youth- adult relationships are observed and analysed in a wide diversity of study environments, from Hull to Sao Paulo, rural Lesotho to Ghana, using varied methods and over different time frames, but with a strong focus throughout on context, practice, impacts and associated ethical considerations. The central concern of the book is not whether young people can produce better knowledge than adults, but rather how to better understand the different knowledges which emerge from diverse actors within different generations in order to ensure that the maximum benefits accrue to children and young people with and for whom the research is conducted. This book was originally published as a special issue of Children's Geographies.