Previous studies suggested that the catecholaminergic systems may be involved in the pathogenesis of attention-deficit hyperactivity disorder(ADHD). Since catechel-O-methyltransferase (COMT) is an enzyme involved in the degradation of catecholaminergic neurotransmitters of the dopaminergic and noradrenergic systems,it is possible that COMT may play a role in ADHD. To test this hypothesis, we used two family-based analyses,the transmission disequilibrium test (TDT) and the haplotype-based haplotype relative risk (HHRR), to examine the possible association between COMT gene and DSM-IV-diagnosed ADHD in a Chinese sample consisting of 79 ADHD probands and their parents. Both TDT (chi2 = 1.03, df=1, P > 0.05) and HHRR (chi2 = 1.08, df = 1, P > 0.05) analyses failed to detect preferential transmission of a COMT allele to the ADHD children. Our data suggested that there was no association between ADHD and the COMT gene in the Chinese population.