Numerous studies have documented relationships between a variety of problem behaviors and academic achievement measures. However, the results of these studies should be interpreted cautiously, given the considerable comorbidity of problem behaviors that often exists among school-age youth. This study addressed the relationships between 8 teacher-reported problem behavior syndromes (withdrawal, somatic complaints, anxiety/depression, social problems, thought problems, attention problems, delinquent behavior, aggressive behavior) and standardized measures of academic achievement (overall, reading, spelling, arithmetic, performance). The sample comprised 41 boys and 17 girls ages I I to 19 years (M = 15.02, SD = 1.90) enrolled in an alternative school. Although withdrawn, somatic complaints, delinquent behavior, and aggressive behavior syndromes exhibited significant zero-order correlations with the academic achievement measures, each of these relationships was mediated by attention problems. A post hoc analysis suggested that the observed association between attention problems and academic achievement was primarily due to the inattention component of the syndrome rather than the hyperactivity-impulsivity component. The findings are discussed with reference to theoretical, research, and treatment implications.