Using a dual trajectory modeling approach, we examined co-occurring trajectories of depression and delinquency from age 11 to age 18 and their relation to adult outcome six years later in a community sample of 1423 (674 boys) adolescents. We also examined the effects of childhood externalizing, internalizing, and social problems on trajectory membership for depression and delinquency. The results showed that although more girls than boys were likely to follow high-level, co-occurring trajectories on depression and delinquency, the adult outcome of adolescents following high-level trajectories on both domains was poorer for boys than for girls. However, the combination of decreasing depression symptoms and increasing delinquency symptoms across adolescence was related with poorer adult outcomes for girls compared to boys. Finally, whereas boys' high-level co-occurring trajectory of depression and delinquency was predicted by childhood aggression, girls' equivalent trajectory was predicted by childhood depression and delinquency. The findings support the "gender paradox" effect (Loeber & Keenan, 1994) stating that in disorders with an unequal gender ratio, members of the gender with the lower prevalence rate tend to be more seriously affected in terms of comorbidity and poor outcome.