This study explored the manner in which poor planning skill impairs reading comprehension of students with ADHD. Ninety-six adolescents with and without ADHD completed a planning task (Tower of London) and answered open-ended questions following the reading of two expository texts under two reading goals - study and entertainment, while their eye-movements were recorded. Findings indicated lower performance for the participants with ADHD on the planning and reading comprehension tests. Moreover, controls exhibited longer and more frequent (re)readings of text ideas in the study than in the entertainment goal condition, whereas readers with ADHD showed similar reading patterns for both reading goals. Critically, the difference observed between the groups on the reading comprehension test was mediated by the difference observed in their planning performance and goal-based reading patterns. Findings suggest that students with ADHD experience difficulties in reading comprehension due to poor planning of their text processing, as appropriate for different reading goals.