PURPOSE: In the CT staging of gastric cancer, the reported size criteria for perigastric lymph nodes (LNs) has varied, as has the accuracy of the findings. We investigated whether relevant criteria could be established for nodal staging by CT, using a new TNM staging system. MATERIALS AND METHODS: In 55 patients who underwent surgery for gastric cancer, lymph node staging was determined by CT, according to various lymph node size criteria. For each patients, a new TNM staging system was used. Two radiologists analyzed the findings and measured the short diameter of discernible perigastric LNs(n=192). Twelve percent (229) were found to be metastatic. For the diagnosis of LN metastasis according to LN size, sensitivity, specificity, and accuracy curves were obtained, and using the McNemar Chisquare test, the results were statistically analysed. RESULTS: The accuracy of lymph node staging was 53% with a size criterion of 8mm, 51% with a criterion of 4mm, and 47% when all discernible LNs were included. These differences were not, however, statistically significant. The size of metastatic LNs in these patients varied widely(1-22mm). Sensitivity and specificity curves crossed when LNs were between 4 and 4.5mm; accuracy was greatest in lymph nodes larger than 7mm. CONCLUSION: The accuracy of N staging by CT, using a new TNM staging system, was low and did not differ significantly according to varying size criteria (McNemar Chi-Square test(p>0.05). This finding may be due to the fact that metastatic lymph node size varied widely.