Fibroepithelial polyps are a rare cause of ureteropelvic junction (UPJ) obstruction in children. Preoperative US diagnosis of fibroepithelial polyps is infrequently reported, with intravenous pylogram and retrograde pyelography being most commonly used for diagnosis. To recommend the most accurate process for diagnosing this disease in children by assessing a modified ultrasonographic procedure for the diagnosis of fibroepithelial polyps. A retrospective review of US and IVP imaging studies performed in surgically and histologically confirmed cases of fibroepithelial polyps in children. Each child was asked to drink as much water as possible 30 min before the US testing. For US, the renal pelvis, UPJ and the proximal ureter were inspected for an echogenic mass resulting in hydronephrosis. For IVP studies, abdominal plain films were performed at 7, 15 and 30 min following contrast injection. Thirty-five children, 34 boys and 1 girl, had confirmed fibroepithelial polyps. The children ranged in age from 3 to 14 years (mean age 9 years). Clinical presentation included intermittent vague abdominal pain (100%) and/or hematuria (9.7%) for a period ranging from 1 month to 5 years. Of the 35 children (37 polyps), 21 (23 polyps) were correctly diagnosed preoperatively with US, establishing a 62.2% (23/37) US accuracy rate. Twenty polyps were seen on the left, three on the right and two children had bilateral polyps. The masses were all mildly echogenic with defined edges. Eight children (9 polyps) had an IVP consistent with fibroepithelial polyps giving IVP an accuracy rate of 24.3% (9/37). US is an effective screening tool for identifying fibroepithelial polyps causing UPJ obstruction in children.