Author contributions: Martinez-Badía J has contributed substantially to the conception and design of the study, acquisition of data from historical sources, drafting the article, and final approval of the manuscript; Martinez-Raga J has contributed substantially to the conception and design of the study, acquisition of data from medical sources, drafting the article, and final approval of the manuscript.Conflict-of-interest statement: Martinez-Badía J reports no conflict of interest. Martinez-Raga J has received fees for serving as a speaker and as an advisory board member for Janssen, Shire, Juste, and Rovi Pharmaceuticals. No sources of funding were used in the preparation, review or approval of this manuscript. Core tip: Attention-deficit hyperactivity disorder (ADHD) is a highly prevalent neurodevelopmental disorder in children and in adults. Although the conceptualization and diagnosis of this disorder is often controversial it is not a modern invention. There are significant published historical medical, and non-scientific reports of individuals with symptoms of inattention, distractibility and over-activity, prior to the 20 th century, since the last quarter of the 18 th century. The present paper explores the early history of ADHD in the medical literature and in other historical sources, to gain better understanding of the roots and evolution of the conceptualization of this disorder.Martinez-Badía J, Martinez-Raga J. Who says this is a modern disorder? The early history of attention deficit hyperactivity disorder. World J Psychiatr 2015; 5(4): 379-386 Available from: