Chapter 3 explores and critically evaluates the main tenets of Childhood Studies by addressing the key concepts of voice, agency, participation and children’s rights. The discussion starts by exploring the challenges of working with child voice, highlighting that voices are messy and multi-layered, heavily influenced by social, cultural and institutional discourses. Like voice, agency must also be understood within intergenerational relationships. A large part of this chapter discusses the differences between the various definitions and descriptions of participation frameworks (e.g. Fielding, 2001; Hart, 1992; Lundy, 2007; Shier, 2001) with a view to draw out actual roles children can take in research studies (such as consultants, partners or researchers in child-led research projects). Similarities and differences between research ‘with’ children and research ‘by’ children are discussed. Addressing opportunities and limitations drawn out of current debates in empirical research, the chapter highlights the most important implications and opportunities for child second language research.