Pediatrics differs from adult medicine in many respects. The obvious body size differences are paralleled by maturational changes. The smaller body of an infant or neonate is substantially different physiologically from that of an adult. Congenital defects, genetic variance, immunology, oncology, and a host of other issues are unique to the realm of pediatrics.

In the U.S., pediatricians are considered to be primary care doctors, along with family practice, internal medicine, and obstetrics. Much of the rest of the world considers them specialists, and parents are only referred to pediatricians for special care not handled by the generalists.