There are three main types of institutions that dominate the lives of youth: coercive (police, courts, and detention centers); developmental (schools and families); and commercial (pinball parlors and retail shops). The relationships that youth have with the agents of these institutions are crucial in any discussion of service use and youth well-being. The law shapes the eligibility and responsibility of children and youth around distinct age markers. The Convention on the Rights of the Child notes the importance of youth's participation in developmental opportunities in an environment conducive to health and well-being. In practical policy terms, such participation is dependent on access and equity, building capacity and resilience, and social inclusion. These features necessary for the participation of youth in constructive developmental activities and experiences are discussed with reference to financial and consumer affairs, education and training, welfare benefits, employment, health, law, criminal justice, family support, and recreation and leisure. The article then considers the nature of services as being specifically for youth and being friendly toward youth. A discussion of the dynamics of service provision advises that the effect of various services and interventions for youth will vary depending upon circumstances and the characteristics of the youth and service providers involved. The article concludes with a brief discussion of service domains. It maintains that service provision can be described and analyzed by reference to specific "ecological" domains; for example, most of the human services and crime prevention literature describe risk and protective factors in relation to the domains of individual, family, peer groups, school, and neighborhood and community. These domains overlap, but nevertheless are discrete from the perspective of causal explanations of behavior as well as service provision site and emphasis. 15 references