Objective: To investigate gender differences in self-reported ADHD symptoms in a group of adults with ADHD and a control group. Methods: A total of 682 adults with ADHD (49.9% females) and 882 controls (59.2% females) completed the Adult ADHD Self-Report Scale (ASRS), listing the 18 symptoms included in the diagnostic criteria of ADHD. Results: Within the ADHD group, females reported more severe symptoms of inattention and hyperactivity/impulsivity than males. This higher symptom report of females was not found in the control group, where the number of severe inattention symptoms rather was higher in males. Conclusion: The results suggest that childhood symptoms of ADHD may have gone unnoticed in girls, emphasizing the need for longitudinal studies of ADHD symptoms across the life span.