We compared four instruments commonly used to screen for and diagnose Attention-Deficit/Hyperactivity Disorder (ADHD) in children. The Bergen Child Study included a DSM-IV ADHD symptom list and the Strengths and Difficulties Questionnaire (SDQ) as screen in Phase one. Phase two included the parent Development and Well-Being Assessment (DAWBA), whereas Phase three comprised in-depth clinical assessment, including the Schedule for Affective Disorders and Schizophrenia for School Aged Children (K-SADS). We compared ADHD as diagnosed by the four instruments in the children with normal intellectual functioning participating in all three phases (N = 234). The DSM-IV ADHD symptom list showed moderate agreement with all other instruments (κ = 0.53–0.57), whereas there was fair agreement between the K-SADS-DAWBA (κ = 0.31) and between SDQ–DAWBA (κ = 0.33). The DAWBA diagnosed fewer children with ADHD than did the other instruments. Implications for use of the instruments are discussed.