According to The American Journal of Psychiatry, there are several sources of controversy around the diagnosis of ODD. One concerns the fact that the DSM-IV criteria differ slightly from those of the World Health Organization's criteria, as outlined in the ICD-10. Diagnosis of ODD is further complicated by the high occurrence of comorbidity with other disorders such as ADHD, though a 2002 study provided additional support for the validity of ODD as an entity distinct from Conduct disorder.
In another study, the utility of the DSM-IV criteria to diagnose preschoolers has been questioned because the criteria were developed using school-age children and adolescents. The authors concluded that the criteria could be used effectively when developmental level was factored into assessment.