This study will determine the nutritional efficacy of Polyunsaturated Fatty Acids (PUFAs) in combination with zinc and magnesium, in children and adolescents diagnosed with Attention Deficit/ Hyperactivity Disorder (ADHD). The nutritional efficacy has to be proven in agreement with the German "Verordnung über Diätetische Lebensmittel (DiätV)" and the corresponding European Directive 1999/21/EC. This objective is reached by performing a placebo-controlled supplementation study with a main efficacy criterion which is also being used in pivotal studies of stimulant and non-stimulant drugs, i.e. the treatment differences between final visit and baseline in the Attention Deficit Hyperactivity Disorder Rating Scale, Parent Version IV (ADHDRS-IV).