This report describes rigorous systematic reviews on the treatment of ADHD, ready for incorporation into evidence-based clinical practice guidelines or performance measures. The report also provides a detailed description of the many limitations of the evidence available and provides recommendations to fill existing knowledge gaps. Studies on ADHD have low reporting quality, methodological flaws, and heterogeneity across outcome measures and tests. A detailed description is included of the many limitations of the available evidence plus recommendations to fill existing knowledge gaps. Fulfilling such knowledge gaps will not be easy and will require genuine collaboration among decision-makers.