There is currently controversy regarding the need for and the effectiveness of behavior modification for children with attention-deficit hyperactivity disorder (ADHD) despite years of study and multiple investigations reporting beneficial effects of the intervention. A meta-analysis was conducted by identifying relevant behavioral treatment studies in the literature. One-hundred seventy-four studies of behavioral treatment were identified from 114 individual papers that were appropriate for the meta-analysis. Effect sizes varied by study design but not generally by other study characteristics, such as the demographic variables of the participants in the studies. Overall unweighted effect sizes in between group studies (.83), pre-post studies (.70), within group studies (2.64), and single subject studies (3.78) indicated that behavioral treatments are highly effective. Based on these results, there is strong and consistent evidence that behavioral treatments are effective for treating ADHD.