In most countries around the world, there has been an increase in the number of children and young people with diabetes. While in general it is relatively easy to distinguish whether a child or teenager has type 1 diabetes or type 2 diabetes, in some cases, young people have elements of both kinds of the condition. This new phenomenon has been labelled ‘double diabetes’ or ‘hybrid diabetes’. Francine Kaufman reports on the existence of double diabetes and the implications of this condition for the initial categorization and treatment of young people who are diagnosed with diabetes.