Idiopathic inflammatory bowel disease in childhood was once considered rare but is now being increasingly recognized. Although ulcerative colitis and Crohn's disease, the two most common types, have some features in common with the adult form, in all of these diseases the differential diagnoses, presentation, and therapy differ in many important ways from those in adults. Infants are also susceptible to diseases not seen in older children. These differences and the often extremely young age of the patient markedly affect the choice and performance of diagnostic imaging techniques. These techniques have to be modeled more to the individual's requirements than in adults, and infants need a different approach even from older children.