What motivates individuals to lie and withhold information from others? There are multiple definitions of dishonest and secretive behavior—ranging from impulsive delinquency to strategic self-preservation, each stemming from different conceptualizations of motivations behind the act. Drawing upon work on agency in both sociology and economics, this dissertation specifies a theoretically grounded explanation of why individuals in general—and adolescents in particular—conceal information from others. Specifically, I propose that—just like adults—adolescents have the capacity to act in any given environment, where that capacity is a function of conscious choice (i.e. deliberative cognitive processes) as well as objective and subjective constraints. When adolescents lie or keep secrets, such information management is both an agentic behavior in-and-of itself, and a behavior that expands one’s future agency (or capacity to act in any given environment), generating more autonomy and control over one’s life. In testing this definition of agentic concealment a) against other theories of secrecy and lying, b) across multiple data sets, and c) with regard to different concealable behaviors, this dissertation improves our understanding of information management. In doing so, it adopts a cross-disciplinary approach, drawing on research in developmental psychology, sociology, criminology, and economics.