This article draws out one of the core reasons why children should be conceived as active agents in research, particularly policy-related research. The main thesis is that policy inevitably projects and, to an extent, constitutes the subject identities of its intended objects--in this case, that of "children". Drawing on several bodies of theory--the "new" sociology of childhood, identity theory, "governmentality" and theories of discourse--the article shows why not incorporating children's voices is a problem for social policy, and suggests that the impact of their exclusion has the potential to render policy both inappropriate and non-responsive.