 This is a 36-week, randomised, double-blind, placebo-controlled trial. The overarching aim of this study is to assess whether a nutritional intervention Omega-3 supplement, when combined with a more traditional treatment approach to conduct disorder and Attention Deficit Hyperactivity Disorder ADHD, is more effective than either approach alone in treating these conditions in children and adolescents. The research questions cannot be answered through alternative means because disruptive behaviour disorders are primarily childhood disorders. 