In this study we did not genotype CA microsatellite in intron 2 in MAO-A gene, but haplotype analysis of the two markers revealed increased transmission of a haplotype consisting of the 3-repeat allele of the promoter VNTR and the G-allele of the 941G/T SNP to ADHD cases, which was driven by the stronger G allele association. Here, MAOA is linked to attention deficit-hyperactivity disorder.