Objectives: Validated instruments to assess ADHD are still unavailable in many languages other than English for teachers, which constitutes a clear obstacle to screening, diagnosis, and treatment of ADHD in many European countries. Method: Teachers rated 892 youths using the ADHD Rating Scale (ADHD-RS). We investigated the factor structure, reliability, and measurement invariance based on confirmatory factor analyses. Results: Results support a bifactor model, including one general ADHD factor and two specific Inattention and Hyperactivity-Impulsivity factors. But the latter is improperly defined calling into question the existence of a Predominantly Hyperactivity-Impulsivity subtype. The measurement invariance is fully supported across gender, age groups, and Gender x Age Groups. Conclusion: Results support the multiple-pathways hypothesis and suggest that a total ADHD score is meaningful, reliable, and valid, as well as specific assessments of Inattention. Some youths—especially older ones—may present a profile of ADHD particularly marked by Inattention symptoms. (J. of Att. Dis. 2013; XX(X) 1-XX)