This study evaluated the fit and criterion validity of a bifactor model for 18 DSM-IV attention deficit/hyperactivity disorder (ADHD) symptoms, along with nine supplementary symptoms that represented the manifestation of inattention and hyperactivity-impulsivity in adolescence and early adulthood. Participants included N = 172 adolescents who were diagnosed with combined type ADHD and who were enrolled in a treatment study. A bifactor model provided reasonably good fit to combined parent- and teacher-reported DSM symptoms and supplemental items at baseline prior to treatment. Across models, the general factor was characterized by high reliability ( = .93, .95), while specific inattentive and hyperactive-impulsive factors were characterized by poor reliability ( = .30-.50). With respect to criterion validity, the general ADHD and specific inattentive factors were uniquely associated with home and school impairment (R-2 = .13-.29) but not adolescent risk-tasking behavior. Results are discussed with respect to the ways in which bifactor models of ADHD inform the diagnostic criteria for ADHD.
