The purposes of the study were to compare academic achievement between children with epilepsy and those with asthma and to identify child perception, school adaptive functioning, and condition severity factors related to academic achievement. Subjects were 225 children (117 with epilepsy and 108 with asthma) aged between 8 and 12 years. Academic achievement was measured using school-administered group tests. Self-report questionnaires were used to measure child attitudes and school self-concept. Teachers rated school adaptive functioning. Data were analyzed using ANCOVA and multiple regression. Children with epilepsy had significantly lower achievement scores than children with asthma. Boys with severe epilepsy were most at risk for underachievement. Factors related to poor academic achievement in both samples were: high condition severity, negative attitudes, and lower school adaptive functioning scores. Less variance was accounted for in the model for epilepsy (R2=0.25) than for asthma (R2=0.36). Boys with high seizure severity were most at risk for achievement-related problems. Future research in epilepsy should consider additional factors in the model predicting academic achievement.