Prevalence, impact, and continuity of self-reported attention deficit disorder (ADD) symptomology from ages 15 to 18 years were examined in a longitudinal study of a New Zealand birth cohort. Method: At age 15, prevalence of ADD symptomology was estimated, with no gender differences found in self-reported symptomology. Four adolescents (0.5%) met full DSM-III criteria for ADD. Adolescents scoring higher than 1.5 SD above the sample mean on total ADD symptom score were identified as having high levels of ADD symptomology. Results: Male and female adolescents reporting ADD symptomology with (6% of males; 4% of females) and without history of behavior disorder (6% of males; 7% of females) did not differ in inattention and impulsivity, received more diagnoses other than ADD, and experienced more adverse educational and social outcomes at 15 and 18 years than did the nonADD group. Conclusions: Findings pertaining to the ADD with history group were consistent with previous research on the outcome of hyperactive children, whereas the ADD without history group may be reflecting the onset of other pathology in adolescence. Results suggest adolescent self-report of attentional difficulties may be a clinically significant marker of adjustment difficulties for both males and females, but additional information likely is needed for accurate diagnosis.