We examined the association between the selected polymorphisms in two candidate 
genes, the arsenite methyltransferase gene (AS3MT, rs11191454) and the 
inter-α-trypsin inhibitors heavy chain-3 gene (ITIH3, rs2535629), and 
attention-deficit hyperactivity disorder (ADHD) in a Korean population. A total 
of 238 patients with ADHD, along with both of their biological parents, were 
recruited. The children were administered intelligence quotient tests, whereas 
their parents completed the Child Behavior Checklist. In the transmission 
disequilibrium test on 181 trios, we found overtransmission of the A allele at 
the AS3MT rs11191454 polymorphism in children with ADHD (χ²=8.81, P=0.003). 
However, there was no preferential transmission at the ITIH3 rs52535629 
polymorphism (χ²=0.14, P=0.707). Our results provide preliminary evidence for 
the overtransmission of the A allele at the AS3MT rs11191454 polymorphism in 
ADHD.