Most research into attention deficit hyperactivity disorder (ADHD) is concentrated on childhood cases, with less of a focus on adolescents and adults (Willoughby, 2003). Individuals with ADHD are likely to experience academic impairment (Barbaresi, Katusic, Colligan, Weaver, & Jacobsen, 2007; Biederman et al., 1996; Loe & Feldman, 2007), however this has mostly been demonstrated in clinic-based childhood studies; non-clinical, adolescent-specific studies are few and far between (Loe & Feldman, 2007). This thesis examines community-based adolescent ADHD symptoms and their influence over academic attainment. The introduction to the thesis provides a background to ADHD and an overview of the literature on influences over academic performance. Chapter 2 consists of a review of the literature on the relationship between ADHD and academic performance, and explores the reasons why ADHD individuals are at an academic disadvantage. Chapter 3 outlines methodological process of the empirical studies of the thesis, which can be found in chapters 4,5, and 6. Chapter 4 is an investigation of the position of ADHD symptoms in the structure of adolescent mental health problems. In Chapter 5, the impact of ADHD symptoms over academic attainment is studied. Chapter 6 examines the role of underlying neuropsychological processes in the relationship between ADHD and academic attainment. Finally, the discussion summarises the findings of each paper and assesses the limitations and implications of the thesis. The core findings are as follows. In Chapter 4, exploratory factor analysis demonstrated that community-based adolescent ADHD symptoms form a valid dimension that is distinct from symptoms of comorbid syndromes. This provides support for the notion that the adolescent ADHD construct is a continuum-based psychopathology. In Chapter 5 regression analysis revealed that ADHD symptoms exerted almost as much influence over academic attainment as general cognitive ability and school-oriented motivation, and far more influence than other forms of psychopathology. Finally, in Chapter 6, it was found that delay aversion and deficient inhibitory control did not mediate the relationship between ADHD symptoms and academic performance. However it should be noted that in the final study, the sample was severely underpowered due to constraints placed on recruitment by the consent process. Overall the results suggest that ADHD symptoms pose a significant academic risk for adolescents, even at sub-clinical levels. Efforts should be made to increase awareness among teachers and carers of the potential plight of adolescents who express symptoms of ADHD.