Objective: Conners Rating Scale (CRS) is frequently used as an auxiliary tool in the diagnosis of Attention Deficit Hyperactivity Disorder (ADHD). Our objective was to study the contribution of CRS to ADHD diagnosis and to show the characteristics on which group (ADHD; control) and DEHB subtype differentiation is based. For this, findings on CRS were compared with those from Behavioral Rating Inventory of Executive Functions (BRIEF), a clinical scale that was specifically developed for ADHD diagnosis. Material and Methods: The study consisted of 160 males within the 72-151 months of age range. There were 122 males in the ADHD (combined subtype: 69, predominantly attention deficit subtype: 37, predominantly hyperactivity/impulsivity subtype: 16) and 38 in the healthy control group. Participants' teachers and parents filled in the forms (rendering 3 scores on subscales of the teacher form and 5 scores on those of the parent form) and BRIEF (rendering 8 scores on subscales of both the teacher and parent forms) (teacher form and parent form each consisting of 8 scores) and submitted them to the researchers. Results: Data were analyzed using analysis of variance, logistic regression analysis and principle component analysis. In both scales, the difference between ADHD and the control group was significant; however none of the scores significantly differentiated subgroups of ADHD. Sensitivity (classification of cases with ADHD to the ADHD group) was high, however specificity (classification of healthy participants to the control group) in especially the CRS parent form was low. The addition of the BRIEF scores to the model did not appreciably alter this finding. CRS was characterized by two factors and grouping occurred according to who did the rating, a finding not justifying the 8 different CRS subtests. Conclusion: Findings suggest that the clinical utility of CRS should be further studied in future research.