Objective: To prospectively investigate prediction of ADHD to anxiety disorders (ANXs) in a national sample of Taiwan. Method: From the Taiwan National Health Insurance Dataset (1997-2007), we collected 2,385 cases of new diagnoses of ADHD from 1999 to 2003 and 9,540 sex-, age- and index dates of the first diagnosis of ADHD-matched cohort controls without ADHD. The outcome is age of the first diagnosis of ANXs until December 31, 2007. Results: More cases of ADHD (17.7%) developed ANXs than did matched controls (1.9%) with a younger age onset (12.7 years vs. 17.9 years) and a shorter "survival time" (1.4 years vs. 5.0 years). Cox models revealed a significant prediction of ADHD to ANXs controlling for other psychiatric comorbidities [Hazard ratio (HR) = 15.83]. The magnitude of such association was greater in males and decreased with older age of first ADHD diagnosis. Conclusion: The findings imply that early detection and treatment for ADHD may offset later development of ANXs. (J. of Att. Dis. 2012; XX(X) 1-XX)