This briefing paper is about children and young people aged 10 to 17 years with mental health problems, learning disabilities and communication difficulties who offend and who are at risk of offending. It seeks to inform local service managers and decision makers about the importance of improving health provision for this vulnerable, and often marginalised, group of children and to provide some pointers towards strategic improvement. The briefing paper should further stimulate debate locally about how professionals and practitioners concerned with children’s services – and with youth justice and health services in particular – can make best use of opportunities presented by NHS reforms and the increased focus on localism. The briefing paper outlines some of the challenges posed in achieving these objectives at a time of great change in the delivery of local authority and health services.