Furthermore, there was a significant difference in the oxy-Hb concentration in the right prefrontal cortex between the ADHD and TD groups (−28.58×10−4±41.37×10−4 a.u. vs. 0.52×10−4±37.58×10−4 a.u.; t = 2.08, P = 0.046). This evidence concerns the gene GSTM1 and attention deficit-hyperactivity disorder.