The present handbook offers a detailed overview of almost the entire range of the developmental disorders with onset in infancy, childhood or adolescence, according to the DSM-IV. Problems like obesity, which do no constitute clinical entities by themselves but may cause important difficulties in children's and adolescents' life are presented as well. This overview is based on the authors' long clinical and research experience in the fields of assessment and treatment of childhood disorders and is supported by the most update evidence of the international scientific literature. Each disorder is included in a different chapter, which is composed by the presentation of the clinical picture, the diagnostic criteria, epidemiological data, and the basic treatment methods for this specific disorder. The transactional nature of the disorders and their interaction with each developmental stage are emphasized. The basic theoretical perspectives are mentioned, with greater importance given to the cognitive-behavioural perspective. The aim of this book is to offer a basic manual for the student of psychology, the clinical child psychologist and every person interested in a comprehensive understanding of the framework in which develop the main childhood disorders that may influence in several degrees a person’s developmental trajectory.