--- - |2 Abstract Autism spectrum disorder (ASD) and attention‐deficit hyperactivity disorder (ADHD) are believed to share the symptom of neurocognitive dysfunction in executive functions. Regarding the components of executive functions, however, dysfunction of motor‐response inhibitory control in children with ASD remains unclear. Thus, using functional near‐infrared spectroscopy (fNIRS), we investigated whether putative inhibitory brain dysfunctions are applicable to children with ASD by adopting a go/no‐go task, which has robustly evoked activation in typically developing (TD) children but not in ADHD children. Twenty‐four ASD and 24 TD children underwent a go/no‐go task, and their cortical hemodynamics were assessed using fNIRS. Relative to TD participants, ASD participants showed reduced activation in the right inferior frontal gyrus and middle frontal gyrus (IFG/MFG) during go/no‐go tasks. The current finding suggests that hypoactivation in the right IFG/MFG during a go/no‐go task would serve as a potential biomarker for identifying children with ASD. - Japanese Psychological Research, Volume 60, Issue 4, Page 251-264, October 2018.