A report of a seminar organised by the Office of Health Economics and the Mental Health Foundation. Child and adolescent mental health services are developing rapidly, yet they cannot meet the huge volume of demand that exists. Recent research has shown an increasing prevalence of mental health problems in children and young people. Mental health problems in children increase demands on social services, education, health and youth justice services, and families. These costs are astronomical when problems are allowed to persist into adulthood. Mental illness is costing the UK ÃÂ£93billion a year, and this is set to rise if we do not intervene. This report describes the findings of a high level seminar on this vital but neglected issue.