Chronic abdominal pain (CAP) in children and adolescents remains one of the pathogenetically ambiguous disorders and a great trouble to their caretakers as well as patients. Although the symptom does not usually lead to a crucial problem, the parents may be terribly worried, the child may be in distress, and the practitioner may be concerned about ordering tests to confirm a serious occult disease. Systemized diagnostic approaches are needed to overcome this unique difficulty. The presence of red flag symptoms or signs is a general indication to pursue diagnostic testing for organic etiologies of CAP on the basis of specific symptoms in an individual case. Functional abdominal pain can be normally diagnosed when there are no red flag symptoms or signs. According to the Rome III criteria for pediatric functional gastrointestinal disorders, functional disorders of CAP can be classified into functional dyspepsia, irritable bowel syndrome, abdominal migraine, and chronic functional abdominal pain syndrome. Cyclic vomiting syndrome and pathologic aerophagia are also major functional causes of CAP. Modern concepts of the pathogenesis of functional abdominal pain include brain-gut interaction, visceral hypersensitivity, autonomic dysfunction, and psychosocial factors. In addition, psychiatric disorders, presented with red flag symptoms or signs, may induce the CAP in children and adolescents. We introduce practical and systemized diagnostic approaches by illustrating clinical cases of CAP in children and adolescents.