Frontal alpha asymmetry predicts inhibitory processing in youth with attention deficit/hyperactivity disorder

•Greater frontal asymmetry during failed inhibition distinguished ADHD from healthy youth.•ADHD youth with greater frontal asymmetry had a greater number of inhibitory errors.•Frontal asymmetry may be a biomarker of cognitive disinhibition among ADHD youth.•The dorsal-lateral prefrontal cortex may be responsible for generating frontal alpha.•Findings support conceptualization of ADHD as an approach-related disorder.