Few follow-up studies have been conducted of girls with ADHD, and none have followed girls into adulthood. The authors sought to estimate the prevalence of psychopathology in girls with and without ADHD followed into young adulthood. The authors conducted a longitudinal case-control study of 6- to 18-year-old girls with (N=140) and without (N=122) ADHD ascertained from psychiatric and pediatric sources. At the 11-year follow-up, 96 (69%) of the girls with ADHD and 91 (75%) of the comparison girls were reassessed (mean age=22 years). Participants were blindly assessed by structured diagnostic interviews. Lifetime and 1-year risks for all composite categories of psychopathology were significantly greater in girls with ADHD grown up relative to comparison girls; lifetime hazard ratios were 7.2 (95% CI=4.0-12.7) for antisocial disorders, 6.8 (95% CI=3.7-12.6) for mood disorders, 2.1 (95% CI=1.6-2.9) for anxiety disorders, 3.2 (95% CI=2.0-5.3) for developmental disorders, 2.7 (95% CI=1.6-4.3) for addictive disorders, and 3.5 (95% CI=1.6-7.3) for eating disorders. For lifetime psychopathology, all six composite categories remained statistically significant after controlling for other baseline psychopathology. Except for addictive disorders, significant 1-year findings remained significant after controlling for baseline psychopathology. The 1-year prevalences of composite disorders were not associated with lifetime or 1-year use of ADHD medication. By young adulthood, girls with ADHD were at high risk for antisocial, addictive, mood, anxiety, and eating disorders. These prospective findings, previously documented in boys with ADHD, provide further evidence for the high morbidity associated with ADHD across the life cycle.