This review summarizes findings on the epidemiology and etiology of anxiety disorders among children and adolescents including separation anxiety disorder, specific phobia, social phobia, agoraphobia, panic disorder, and generalized anxiety disorder, also highlighting critical aspects of diagnosis, assessment, and treatment. Childhood and adolescence is the core risk phase for the development of anxiety symptoms and syndromes, ranging from transient mild symptoms to full-blown anxiety disorders. This article critically reviews epidemiological evidence covering prevalence, incidence, course, and risk factors. The core challenge in this age span is the derivation of developmentally more sensitive assessment methods. Identification of characteristics that could serve as solid predictors for onset, course, and outcome will require prospective designs that assess a wide range of putative vulnerability and risk factors. This type of information is important for improved early recognition and differential diagnosis as well as prevention and treatment in this age span.