Objective: To examine self-reported positive affect (PA) and negative affect (NA) among youth with ADHD (only and comorbid) and other non-ADHD-referred youth in an ethnically diverse clinical sample. Method: Semi-structured interviews identified 80 pure ADHD, 284 ADHD plus one or more comorbidities, and 730 non-ADHD youth (e.g., other diagnoses or no diagnosis). The Positive and Negative Affect Scale–Children (PANAS-C) was used to assess affective states. Results: Even after controlling for the influence of potential confounds, youth with only ADHD reported higher PA and lower NA than other clinic-referred youth. The ADHD-comorbid group reported higher PA than the "non-ADHD" group, but these groups did not differ on level of NA. ADHD subtype did not influence results. Conclusion: Among clinic-referred youth, ADHD is associated with higher levels of PA and when there are no comorbid disorders, lower levels of NA. (J. of Att. Dis. 2013; XX(X) 1-XX)