Objective: This study aimed to objectively assess signs of hyperactivity in adults suspected of having ADHD, addressing potential sex bias in diagnosis. Methods: About 13,179 (49% female) adults with an average age of 33 years with ADHD and 1,910 (41% female) adults with an average age of 36 years without ADHD were included. Motor activity was measured using the Quantified Behavioral Test, analyzing "provoked," and "basal" activity. Sex by group differences were analyzed using analysis of variance. Results: Results showed significant ADHD effects on the basal and provoked activity measures, while sex effects were only notable for provoked activity. Males, irrespective of diagnosis, exhibited higher provoked activity than females, while both sexes with ADHD displayed approximately twice the basal activity and about three times the provoked activity compared to their respective sex controls. Conclusion: These findings suggest that females with ADHD suffer equally from hyperactivity compared to males, challenging the notion of a sex-dependent presentation of hyperactivity. This may lead to more accurate and timely diagnoses, reducing ADHD-related burdens and comorbidities in females. (J. of Att. Dis. 2024; 28(12) 1589-1597)