This chapter focuses on the ideas about the emotional health of children and young people. It examines the risk and protective processes involved in child and adolescent mental health. The chapter presents a range of interventions that have been shown to make a difference. It considers the perspectives of young people on common mental health difficulties and the stigma that surrounds them, as well as approaches that aim to overcome prejudice and ignorance about mental health. The chapter describes the internalization of emotional and behavioural difficulties, in depression and anxiety, and their externalization through aggressive and disruptive behaviour. Research into self-harm and suicide in children and adolescents presents a particularly disturbing illustration of the urgent need to address mental health issues as early as possible in the young person’s life and to be alert to the signs and symptoms as they emerge.