Background: Vesicoureteral Reflux (VUR) is the back flow of urine from the bladder into the ureter and kidney mainly due to the failure of the normal function of valve at the junction of the ureter to the bladder. Ureteral reflux is an important risk factor for renal scarring in patients with or without urinary tract infection. In long term, renal scarring may lead to secondary hypertension and chronic renal failure. Early detection of VUR has an important role in the prevention of these complications. Radiographic cystography (VCUG) and isotope cystography (DRNC) are two common methods for detection of VUR. In some patients with strong evidence of VUR in clinical finding, ultrasound and DMSA, VCUG is normal. For this reason and the overall higher sensitivity of DRNS in detection of reflux, this study compared the result of VCUG and DRNC in patients who had evidence of VUR, but had normal VCUG.Methods: In this study, 35 children (5 males, 30 females) with urinary tract infection and normal VCUG who had hydroureteronephrosis in ultrasound (without evidence of obstruction in the urinary tract), significant involvement in DMSA scan or recurrent urinary tract infections had undergone isotope cystography (DRNC).Findings: After DRNC among 70 ureteral units, reflux was observed in 33 units. There were mild reflux in 17 units (51%), moderate reflux in 14 ureteral units (42%) and sever reflux in 2 units (6%). In 29 units of the 33 refluxing units, positive findings compatible with renal involvement in DMSA renal scan were observed.Conclusion: This study showed that the DRNC is more sensitive in detecting VUR than VCUG. Therefore, in patients with normal VCUG and high suspicion of VUR using DRNC is helpful. Although larger studies are necessary for this recommendation.