This paper describes current knowledge and opinions on Attention-Deficit/Hyperactivity Disorder. The aetiology, phenomenology and clinical course of this illness, methodological difficulties in assessment of its prevalence, as well as treatment options and outcome are overviewed in respect of updated literature. Some social, familiar and economic contexts of ADHD are discussed. Special emphasis is put on diagnostic issues and psychological therapy and counselling, since the prevalence (approx. every twentieth child) and the lack of professionals has moved those crucial medical activities from child and adolescent psychiatrists to general physicians.