Radiologic evaluation of the genitourinary tract in infants and children frequently focuses on the kidneys. The bladder may be imaged in a cursory or perfunctory manner or not at all. Unfortunately, this practice contributes to errors in diagnosis of renal abnormalities both prenatally and throughout childhood. For example, a "renal cyst" diagnosed prenatally really might be the obstructed upper pole of a duplex kidney; scanning the bladder is necessary to detect the dilated distal ureter or ureterocele below. Similarly, the bladder might have a congenital anomaly when the kidneys are normal. The appearance of many common and a few uncommon bladder anomalies in children are described in this article. Some normal variants and acquired problems, such as tumors and neurogenic bladder, are discussed and illustrated because these can cause problems in diagnosis. Changes in the appearance of the bladder produced by surgery to correct vesicoureteral reflux are also presented.