Attention-deficit/hyperactivity disorder (ADHD) is a commonly occurring behavioral disorder among children. Community-based physicians are often the primary providers of services for children with ADHD. A set of consensus guidelines has been established that provides best practice diagnostic procedures for primary care physicians. These assessment recommendations emphasize the importance of collecting parent and teacher rating scales, using Diagnostic and Statistical Manual of Mental Disorders IV criteria as the basis for making an ADHD diagnosis, and evaluating for comorbid conditions. The ADHD diagnostic process is complicated by several factors including the subjectivity of the ADHD diagnosis, differential diagnosis with comorbid conditions, and the inconsistent manifestation of ADHD symptomatology across development. The present article provides recommendations for addressing these complex diagnostic issues. ADHD assessment methods and tools, the process of assessing for comorbid conditions and making differential diagnosis, and when to make a referral to specialists are reviewed.