We found no significant effect of COMT on ADHD (F(2.460) = 1.537; p = 0.216; partial eta-squared = 0.007; covariates: sex: F(1.460) = 16.248; p < 0.001; partial eta-squared = 0.034; conduct problems: F(1.460) = 94.844; p < 0.001; partial eta-squared = 0.172). Here, COMT is linked to attention deficit-hyperactivity disorder.