Congenital anomalies of the kidney and urinary tract are the commonest congenital anomalies in children, often detected prenatally with ultrasound. This method is useful for assesing the degree of dilatation of the collecting system, structure of the kidney parenchyma, amount of amniotic fluid and urinary bladder. Hydronephrosis is the most common among them. Anomalies can be bilateral or unilateral and different defects may coexist in an individual child. Anomalies of other organs and organ systems are often associated with anomalies of the kidneys and urinary tract, described in numerous syndromes. Congenital anomalies of the kidney and urinary tract can be divided in anomalies of the renal parencyma development, renal embryonic migration and position, cystic kidney diseases and anomalies of the urinary tract (collecting system of the kidneys, ureters, urinary bladder and urethra). They are the commonest cause of end-stage renal disease in children.