Attention-deficit hyperactivity disorder (ADHD) belongs to common causes of psychiatrie treatment in childhood. Risk factors of the pathogenesis are not only genetic factors, but also non-genetic ones such as low weight at birth, perinatal hypoxia and influence of toxic substances during the prenatal period. The causes of the disorder háve been thoroughly investigated using the neuroimaging and molecular biology methods in the past ten years. It was found that biological parents and relatives with ADHD háve much higher percentage of ADHD symptoms in their offsprings. Obviously, the results of twin studies háve brought the evidence of the disorder's heritability. During the past few years many molecular-biology studies háve appeared, which are focused on the research of influence of so-called candidate genes in the pathogenesis of ADHD. Our review summarises the results of the¬se studies.

        Key words: ADHD, hyperkinetic disorder, association study, polymorphism, gene, DRD2, DRD4, COMT, DBH, DAT1, NET1, MAO, IL-