Objective: This study evaluated the association between attention-deficit/hyperactivity disorder (ADHD) and psychometrically defined cognitive variables across the adult life span, using data from a large controlled study of adults with and without ADHD. Method: Comparisons were made between 2 groups of adults: participants with DSM-IV-diagnosed ADHD who had never received pharmacotherapy for their ADHD (n = 116) and 146 control participants. Subjects received a battery assessing IQ, neuropsychological measures, and academic testing. We modeled cognitive measures as a function of age and group status using linear regression. The study was conducted at Massachusetts General Hospital, Boston, between 1998 and 2003. Results: ADHD and control subjects maintained similar, statistically significant differences in all psychometrically assessed measures of cognition within each decade that was represented (all P values < .01). Conclusion: The negative impact of ADHD on multiple, nonoverlapping, psychometrically assessed measures of cognition remained constant across the life cycle, suggesting that the association between ADHD and cognition neither improves nor deteriorates across the life cycle.