Attention-deficit hyperactivity disorder(ADHD) is a complex, heterogeneous and multifactorial neurodevelopmental disorder characterized by persistent symptoms of inattention, hyperactivity and impulsivity. Although the first clinical description of a constellation of symptoms highly resembling to what currently could be diagnosed as ADHD is generally attributed to George F Still in 1902, there are scattered but significant published historical medical, scientific and non-scientific reports, much prior to Still’s lectures, of what is currently conceptualized as ADHD. The present report aimed at exploring the early history of ADHD, prior to the 20~(th) century in the medical literature and in other historical sources, to provide clinicians, researchers and other professionals with a better understanding of the roots and current conceptualization of this disorder. It is possible to find clues and highly suggestive descriptions of individuals presenting symptoms resembling what is currently defined as ADHD in the literature, in paintings or in the Bible. However, the earliest medical reports of individuals with abnormal degrees of inattention, distractibility and overactivity date from the last quarter of the 18~(th) century, included in two of the first textbooks specifically on the subject of mental diseases, published by the German Melchior Adam Weikard and the Scottish Sir Alexander Crichton. During the 19~(th) century some eminent physicians from Germany, France or Great Britain, such as Charles West, Thomas C Albutt, Thomas S Clouston, William W, Ireland, John Haslam, Heinrich Neumann, or Désiré-Magloire Bourneville, among others provided clinical depictions of patients that most likely presently would be diagnosed as having ADHD. Whilst some of the children described by Still and his predecessors may have suffered from a variety of neurological and psychiatric disorders, many of these patients showed clear symptoms of ADHD and may present with comorbid disorders, as it is commonly the case in clinical practice. Attention-deficit hyperactivity disorder (ADHD) is a complex, heterogeneous and multifactorial neurodevelopmental disorder characterized by persistent symptoms of inattention, hyperactivity and impulsivity. Although the first clinical description of a conslity of symptoms highly resembling to what is could could be be diagnosed as ADHD is generally attributed to George F Still in 1902, there are scattered but significant published historical medical, scientific and non-scientific reports, much prior to Still’s lectures, of what is currently conceptualized as as ADHD. The present report aimed at exploring the early history of ADHD, prior to the 20th ~ (th) century in the medical literature and in other historical sources, to provide clinicians, researchers and other professionals with a better understanding of the roots and current conceptualization of this disorder. It is possible to find clues and highly suggestive descriptions of individuals presenting symptoms resembling what is currentl y defined as ADHD in the literature, in paintings or in the Bible. However, the earliest medical reports of individuals with abnormal degrees of inattention, distractibility and overactivity date from the last quarter of the 18th ~ th century, included in two of the first textbooks specifically on the subject of mental diseases, published by the German Melchior Adam Weikard and the Scottish Sir Alexander Crichton. During the 19 ~ (th) century some eminent physicians from Germany, France or Great Britain, such as Charles West, Thomas C Albutt, Thomas S Clouston, William W, Ireland, John Haslam, Heinrich Neumann, or Désiré-Magloire Bourneville, among others provided clinical depictions of patients that most likely presently would be diagnosed as having ADHD. Whilst some of the children described by Still and his predecessors may have suffered from a variety of neurological and psychiatric disorders, many of these patients showed clear symptoms of ADHD and may present with comorbid disorder s,as it is commonly the case in clinical practice.