This study investigated the role of inattention and working memory in predicting academic achievement in 145 adolescents aged 13 to 18 referred for attention deficit/hyperactivity disorder (ADHD). Path analysis was used to examine whether auditory-verbal and visual-spatial working memory would mediate the relationships between classroom inattention symptoms and achievement outcomes. Results provide support for the mediational model. Behavioral inattention significantly predicted both auditory-verbal and visual-spatial working memory performance. Auditory-verbal working memory was strongly associated with adolescents' achievement in reading and mathematics, while visual-spatial working memory was only associated with achievement in mathematics. The path from inattention symptoms to reading was partially mediated by the working memory variables, but the path from inattention to mathematics was not mediated by working memory. The proposed model demonstrated a good fit to the data and explained a substantial amount of variance in the adolescents' achievement outcomes. These findings imply that working memory is a risk factor for academic failure for adolescents with attentional problems.