Aim: The purpose of this study was to determine the validity of the observation that obviously overweight children/adolescents did not comply with orthodontic directives when compared to a control group of not obviously overweight children. Methods: A total of 1286 patient records were reviewed independently by three evaluators. All evaluators had to agree that the patient was not only overweight, but obviously overweight. Slakters Orthodontic Patient Cooperation Scale was used to determine the degree of noncompliance. A chi-square test was used to analyze the findings and indicated that 51% of the obviously overweight group were uncooperative, compared to 28% of the control group, establishing a highly significant relationship (P = 0.01) between obviously overweight patients and noncompliance with orthodontic treatment. Results: Nearly twice as many obviously overweight patients, when compared to controls, were judged to be noncompliant to the extent that it affected the treatment plan. This finding is more significant than any other behavioral or social indicator explored in the orthodontic literature. Conclusion: Clinicians should be cautious in assuming reasonable cooperation when selecting a treatment plan for the obviously overweight child/adolescent patient. World J Orthod 2001;2:69–72.