Objective: To examine the relationship between dietary patterns and ADHD in a population-based cohort of adolescents. Method: The Raine Study is a prospective study following 2,868 live births. At the 14-year follow-up, the authors collected detailed adolescent dietary data, allowing for the determination of major dietary patterns using factor analysis. ADHD diagnoses were recorded according to International Classification of Diseases, 9th Revision coding conventions. Logistic regression was used to assess the relationship between scores for major dietary pattern and ADHD diagnoses. Results: Data were available for 1,799 adolescents, and a total of 115 adolescents had an ADHD diagnosis. Two major dietary patterns were identified: "Western" and "Healthy." A higher score for the Western dietary pattern was associated with ADHD diagnosis (odds ratio = 2.21, 95% confidence interval = 1.18, 4.13) after adjusting for known confounding factors from pregnancy to 14 years. ADHD diagnosis was not associated with the "Healthy" dietary pattern. Conclusion: A Western-style diet may be associated with ADHD. (Contains 3 tables.)