In daily practice, mental health professionals working with children and adolescents are faced with the responsibility of recognising and managing psychiatric symptoms of organic origin, with diagnosable physiopathology and aetiology by means of a clinical examination and appropriate complementary studies. The patient's evolution and prognosis depend on timely and specific diagnosis and treatment. This book describes the most frequent psychiatric conditions of medical origin and their possible causes, lists the general characteristics of their evaluation and treatment guidelines. Interdisciplinary and team work is essential, involving mental health, paediatrics, neuropaediatrics and all the necessary specialists according to the underlying pathology.