 The study involves children and adolescents diagnosed with disruptive behaviour disorder DBD, i.e. conduct disorder or oppositional defiant disorder or attention deficit hyperactivity disorder ADHD, i.e. combined type or ADHD predominantly inattentive type or ADHD predominantly hyperactive-impulsive type. 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 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. 