Objective To evaluate the value of 3-D reconstruction in multi-detector spiral CT urography (MDCTU) for diagnosing upper urinary tract diseases (UUTDs) by means of both diagnostic sensitivity and ROC curve. Methods A total of 41 patients with UUTD were collected. All of them took MDCTU as well as reconstructions including MPR, MIP and VR. Compared with golden standards, the diagnostic value of MDCTU, MPR, MIP and VR were evaluated using both diagnostic sensitivity and ROC curve. Results a) A total of 49 upper urinary tract lesions were detected in those 41 patients; b) For UUTD, the localization diagnostic sensitivities of MPR, MIP, and VR were 48/49 (98.0%), 27/49 (53.2%), and 19/49 (38.8%), respectively; while their qualitative diagnostic sensitivities were 47/49 (95.9%), 17/49 (34.7%), and 13/49 (26.5%), respectively; the differences between MPR and the others were significantly (Plt;0.05); c) For distinguishing benign from malignant lesions, the Az value (area under ROC curve) of MPR, MIP, and VR were 0.998, 0.736 and 0.669, respectively; the differences between MPR and the others were significant (Plt;0.05); and d) MPR was completely the same as MDCTU in both diagnostic sensitivity and Az value. Conclusion The common 3-D reconstructions in MDCTU were different in value. MPR is highest in the diagnostic efficiency, which is similar to MDCTU, and is regarded as the basis of diagnosis; while MIP and VR are more stereo and intuitive. So it shows that the comprehensive application of CTU 3-D reconstructions has important value for diagnosing UUTD and distinguishing benign from malignant.