This book is a comprehensive guide to ADHD, which has emerged as the most discussed neurodevelopmental disorder of our time. Through its pages, a critical presentation of the current scientific knowledge about the nature, diagnosis, and therapeutic management of this disorder is attempted, with an extensive, in-depth study of international and Greek literature. In this effort, the authors of the book utilize their many years of clinical experience with individuals with ADHD and their families at the Developmental and Learning Difficulties Psychological Center "ARSI". They also propose a new framework for the diagnosis and therapeutic management of ADHD, the multidimensional approach, which is based on the basic principles of cognitive-behavioral theory and the developmental model of psychopathology. The authors approach this disorder from the perspective of the researcher, the academic teacher, and, above all, the psychologist, who experiences on a daily basis in clinical practice the anxiety, difficulties, problems, and concerns of children with ADHD, young adults with the disorder, their parents, friends, and teachers. This guide can serve as a primary source of information for parents and an important tool for educators who need specialized knowledge and techniques in order to manage the various learning and behavioral difficulties of these children. Additionally, it can be utilized at a clinical level by professionals of various specialties in the field of mental health, as it includes the structured description of the diagnostic process as well as a complete early intervention and therapeutic management program for ADHD from preschool age to adulthood.