A growing body of evidence suggests that youth with Intellectual/Developmental Disabilities (IDD) are at significantly higher risk of developing mental illness than other peers. Diagnosing and treating children and teens with IDD can be more difficult than diagnosing adults and/or neurotypical peers. In addition, there are a variety of services frequently provided these children, including disability supports and Applied Behavior Analysis (ABA) in addition to clinical treatment. This seminar will review services commonly offered to youth dually diagnosed with IDD and mental illness, discuss strategies to adapt treatment to meet the needs of this population, and provide an overview of integrating these services through case illustrations [Elective for Child/Adolescent Mental Health or Developmental Disabilities Certificate Program]