The authors discuss the anatomical, clinical, and US patterns of 5 cases of urachal cysts observed in pediatric patients (average age: 9.2 months) over the last 4 years. All cases had surgical confirmation. Linear and convex probes with 3.75, 5, and 7.5 MHz frequency were employed. Most of the observed lesions were oval in shape, their size ranging 3-6 cm; they were found in ventral-epivesical regions and had no mobility. Liquid echotexture with hyperechoic deposits on the lower layers was observed in 2 cases, and inhomogeneous solid or complex mass-like echotexture in 3 cases (suppurated cysts). Differential diagnosis includes mesenteric cyst, simple and teratomatous ovarian cyst, bladder diverticulum and hydrometrocolpos. Echotomography exhibited high accuracy in detecting this kind of lesion and allowed guidance of percutaneous drainage for the preoperative treatment of infected cysts. Both cystography and CT appeared to be useless.