Objective: To investigate the characteristic findings in CT images associated with N-staging of rectal carcinoma. Methods: Fifty nine patients underwent radical resection for rectal carcinoma after preoperative CT examinations. pN0, pN1, and pN2 were classified based on the pathological examination of excised specimens according to the AJCC N-staging criterion. Images were reviewed by two radiologists using CT cine blindly, reaching a consensus on size, number and distribution of lymph nodes, serosa behavior and circumferential infiltration of rectal carcinoma. The relationship between lymph node metastases and CT findings was analyzed statistically with SAS using k-w test and x2 test. Results: Lymph nodes were depicted in all node-positive cases. The mean diameters of the largest nodes displayed in the groups of pN0, pN1, pN2 were 3.84 mm, 5.60 mm and 6.79 mm respectively; the diameters showed a statistically significant increase with N-stage developing (H=23.842, P<0.01). The mean numbers of lymph nodes in the groups of pN0, pN1 and pN2 were 3.0, 4.5 and 9.0 respectively, which also showed an increasing trend and significant differences from each other (H=21.834, P<0.01). The summation diameters of all depicted nodes also showed a significant difference in the N0, N1 and N2 groups (H=32.037, P<0.001). Positive nodes were seen in 25% (3/12) of cases with perirectally displayed nodes, in 58.6%(17/29) of cases with lymph nodes distributed both perirectally and along the superior rectal artery, and in 72.7%(8/11) of cases with nodes detected along iliac vessels combined with either one of the previous two distributions patterns. The distribution patterns of lymph nodes were significantly different in N0, N1 and N2 groups (x2=19.517, P<0.05). The disorder of serosa behavior and circumferential infiltration of rectal carcinoma were more likely to occur in node positive group than negative group with statistical significance (x2=8.979, P<0.01, x2=5.107, P<0.05). Conclusion: Comprehensively considering the size, number, distribution of depicted lymph node, as well as serosa disorder and circumferential infiltration of rectal carcinoma would be helpful for improving the N-staging of CT in patients with rectal carcinoma preoperatively.