Attention deficit hyperactivity disorder (ADHD) is a common, long-lasting, and highly impairing childhood-onset neuropsychiatric disorder. Cross-sectional (1) and longitudinal (2) studies have provided strong evidence to support the relationship between ADHD symptoms/diagnosis and educational attainment/academic achievement. Although more than a dozen prospective studies have examined such a relationship (2), only two studies, which included both core symptoms (3, 4) or ADHD subtypes (4), attempted to distinguish the effects from inattention and hyperactivity symptoms. Lee and Hinshaw (3) found that 5-year follow-up academic achievement was predicted only by inattention symptoms assessed at the ages of 6–13 years in both ADHD and comparison samples. Massetti et al. (4) reported that the inattentive group in an 8-year follow-up study was more likely to have academic underachievement. However, the confounding effects from combined conditions of learning disability and internalizing symptoms were not controlled in their analysis. Because of high collinearity of inattention and hyperactivity/impulsivity symptoms, the effect of either core symptom may be partially explained by the other core symptom. It would be necessary to include the three symptom dimensions of ADHD in one study to examine the specificity of this relationship in order to help identify the possible mechanisms linking ADHD to educational outcome and to develop specific measures for prevention of school failure. However, because of the instruments used to assess ADHD symptoms, some prospective studies have only reported information on inattention symptoms (e.g., measured by the Teacher's Report Form [5, 6] or Child Behavior Checklist ), hyperactivity symptoms (e.g., measured by the Conners Rating Scales-Revised  or Rutter “A” Health and Behavior Checklist ), or ADHD diagnosis (e.g., references 3, 4, 9), preventing the authors from conducting further analysis of the unique effects of the two core symptoms. Investigation of the specificity of the association between ADHD symptoms and academic achievement that includes both inattention and hyperactivity/impulsivity symptoms in one study is needed. Only two prospective clinical-based studies have done so as yet, but neither study included enough controls for confounders (3, 4).