Objective: In this study, we investigate the differences between parent and teacher ADHD ratings, and how these ratings relate to perceived stress in children with ADHD. Method: Ratings by parents and teachers with the Swanson, Nolan and Pelham ADHD symptom rating scale (SNAP-IV) were collected from children with a clinical diagnosis of ADHD (n = 137). Also, information on medication was collected. Children (≥11 years of age; n = 64) were invited to complete the Pressure-Activation-Stress scale. Results: Among girls, but not boys, teacher ratings were significantly lower than parental ratings on all symptom scales. Lower teacher ratings on hyperactivity symptoms were associated with higher levels of perceived stress. Conclusion: The findings suggest a potential gender bias in ratings among teachers. Underrated, and hence underidentified, ADHD problems in the school setting seem to increase the perception of stress in the sense of pressure for both girls and boys.