Attention‐deficit hyperactivity disorder (ADHD) is a risk for learning. Because ADHD commonly includes behaviours of inattention and behaviours of hyperactivity/impulsivity, how the two types of behaviours independently affect children’s academic competence remains poorly understood.

To investigate the impact of behaviours of inattention and behaviours of hyperactivity/impulsivity on Chinese students’ academic competence.

Parents of 167 preschoolers (Cohort 1), parents of 313 first graders (Cohort 2), and 1,003 high school students (Cohort 3).

The ADHD‐RS‐IV Preschool version (Cohort 1), ADHD‐RS‐IV Home version (Cohort 2), and BASC‐SRP (Cohort 3) were used to measure behaviours of inattention and hyperactivity/impulsivity. Academic competence was operationalized as school readiness (Cohort 1), math and language arts scores at two time points provided by school (Cohort 2), and self‐reported academic performance (Cohort 3). Multiple regressions were performed to investigate the relationship between academic performance and behaviours of inattention alone (Step 1), and behaviours of hyperactivity/impulsivity alone (Step 2), and behaviours of inattention together with behaviours of hyperactivity/impulsivity (Step 3).

For each cohort, both types of behaviours were negatively correlated with academic competence. However, regression analyses showed that in Step 3, behaviours of hyperactivity/impulsivity either failed to predict academic competence or predicted better academic competence. Overall, behaviours of inattention alone accounted for a similar amount of variance in academic competence as did behaviours of inattention and hyperactivity/impulsivity combined.

Behaviours of inattention presented a risk for academic competence but the effect of behaviours of hyperactivity/impulsivity varied. Implications for instructional strategies for behaviours of inattention were discussed.