Health psychology has grown remarkably, encompassing populations of all ages, which generated the need to intervene in the health-disease process in childhood and adolescence. This area deals with the practice, education, training, and research of the relationship between the physical and psychosocial health of this age group, with the aim of promoting, preventing, maintaining, rehabilitating, and providing holistic care from the prenatal stage to early adulthood to patients, families, and specialist professionals in the pediatric area. Despite its importance, this area still faces great challenges, such as the scarcity of specialized literature and the lack of a unifying theoretical framework. In the chapter 22, we describe its general characteristics, we offer a brief historical and current review of works published in the area highlighting key issues such as therapeutic adherence, drug use, etc., in turn, we underline the need to address both highly prevalent diseases such as cancer or obesity; as well as diseases considered rare. We discussed the need for a multi- and interdisciplinary collaboration to improve the response to the needs of the child and adolescent population and promote the training of specialized professionals, in order to integrate a robust theoretical model.