Attention deficit hyperactivity disorder, is most commonly studied and diagnosed psychiatric disorder, affecting 2-13% of children globally. Mineral status among children with attention deficit hyperactivity disorder has been the subject of several clinical trials. Magnesium deficiency is the most common mineral deficiency associated with attention deficit hyperactivity disorder. In this book, authors will review the history of attention deficit hyperactivity disorder, clinical picture, etiology as regard biological and neuropsychological basis, epidemiology, risk factors, assessment and treatment options. Nevertheless, explanation about the role of magnesium in the treatment of attention deficit hyperactivity disorder and the method that those children can be supplied either naturally or as a supplement. Finally, the authors ended up the book by a short follow up study about the rate of magnesium deficiency in attention deficit hyperactivity disorder, and the effect of its supplementation in deficient children as an add on therapy. Magnesium supplementation proved useful as adjuvant treatment in magnesium deficient children with attention defciit hyperactivity disorder.