Ultrasound the most popular examination in children with urinary tract infections allowing early detection of defects in the urinary tract. One of malformations which can be the reason of urinary tract blockage is megaureter. Majority of authors consider ureters wider than 7 mm as megaureters. Megaureters could be divided into primary and secondary depending on the reason. Suspected megaureter should be diagnosed to determine the cause and to plan the treatment to prevent infections and progressive damage of kidney function. Ultrasound of the abdomen and urinary tract remains a basic test. Voiding cystourethrogram is the second most frequent examination. It enables, among others, to diagnose vesico‑ureteral reflux. It is also advisable to perform renoscintigraphy which allows to asses renal function and determine the degree of urine flow disorder. It is estimated that nearly 80% of megaureters do not require intervention, as the problem subsides spontaneously. 15–20% of children with megaureter require surgical treatment. Surgical treatment involves resection of the distal, tapered section and transplantation of ureter to a new location within the bladder triangle. The common goal of all those methods is to obtain a long, submucosal part of ureter, as a protection against vesico‑ureteral reflux.