Objective: We sought to examine preliminary results of brain alterations in anterior cingulate cortex (ACC) in treatment-naive adults with ADHD. The ACC is a central brain node for the integration of cognitive control and allocation of attention, affect and drive. Thus its anatomical alteration may give rise to impulsivity, hyperactivity and inattention, which are cardinal behavioral manifestations of ADHD. Method: Segmentation and parcellation of the ACC was performed on controls (n = 22), treated (n = 13) and treatment-naive adults with ADHD (n = 13). Results: There was a 21% volume reduction in the left ACC of the treatment-naive group relative to the control group. Also, there was a 23% volume reduction in the right ACC of the treated group relative to the control group. Conclusion: These results raise the possibility that in ADHD there are volumetric deficits persistent into adulthood, that are independent of medical treatment. (Contains 1 figure and 2 tables.)