Obesity rates throughout the world have risen rapidly in recent decades, and are now a leading cause of morbidity and mortality. Several studies indicate that behavioral and affective distress in childhood may be linked to elevated adult body mass index (BMI). The present study utilizes data from a 20-year longitudinal study to examine the relations between symptoms of conduct disorder, attention-deficit/hyperactivity disorder, and depression during late childhood and mid-adolescence and BMI during emerging adulthood. Data were analyzed using multiple regression. Results suggest that childhood and adolescent problems may influence adult BMI through direct impacts on adolescent overweight, a condition which then persists into adulthood.