Caliceal diverticulum is a rare disorder in which a urine-filled cavity is connected to the renal calix by a narrow isthmus. Treatment of caliceal diverticulum varies depending on the complications, which include recurrent kidney infections, hematuria, and symptomatic calculi. The use of sonography may be insufficient for accurately diagnosing this condition; contrast urography, CT, or both also may be needed. We report the cases of 2 pediatric patients whose initial sonographic diagnosis was renal cystic disease but whose final diagnosis was caliceal diverticulum on contrast-enhanced urography in 1 case and both urography and CT in the other case. The patients received no further treatment but continue to receive follow-up care to monitor for the presence of infections and calculi. Accurate diagnosis of caliceal diverticulum in both cases spared the patients and their families the psychological burden of unnecessary further investigation of renal cystic disease. These cases emphasize the importance of using contrast-enhanced imaging modalities for confirmation when sonographic findings suggest the presence of renal cystic lesions. (C) 2003 Wiley Periodicals, Inc.