Computed Tomography (CT) is an indispensable noninvasive method for staging transitional cell carcinomas of renal pelvis and ureter. Twenty-seven patients with upper urinary tract tumors were examined and the CT results correlated with histopathologic findings. These tumors exhibit three different development patterns: in our series we identified 17 intraluminal sessile lesions, 6 focal or concentric wall thickenings and finally 7 infiltrating masses; soft-tissue density lesions exhibited in all cases mild contrast enhancement (mean density increase: 38 HU). Even though the attenuation values of tumors do not allow the accurate demonstration of the depth of renal pelvis and ureteral wall invasion, CT can differentiate the lesions which are still confined within the external wall layers (CT1, 17 cases) from those invading the peripelvic-ureteral fat (CT2, 9 cases) or spreading to other organs as well as distant metastases (CT3, 4 cases). Delayed scans can also demonstrate intraluminal lesion extent and sometimes changes of patients' position allow better differentiation of wall outlines from peripheral fat. The overall staging accuracy of CT was 76.66% and its sensitivity was 93.33%. The assessment of lymph node metastases was the major cause of error in the CT evaluation of these tumors.