BACKGROUND/AIMS: The purpose of this study was to find the factors predicting the neoplastic polyp of gallbladder and analyze the size criteria associated with malignancy. METHODS: A total of 354 subjects with gallbladder polyps confirmed by tissue pathology were included for the analysis. The clinical and radiological features of the polyps were compared between the two groups (neoplastic vs. non-neoplastic) and in the three groups (non-neoplastic vs. adenoma vs. adenocarcinoma). The independent factors associated with malignancy were studied. RESULTS: Of 354 patients, non-neoplastic polyps were observed in 229 (64.7%) patents, adenoma in 85 (24.0%) and adenocarcinoma in 40 (11.3%). The mean diameter of non-neoplastic polyp, adenoma, and adenocarcinoma were 11.3+/-2.8 mm, 16.0+/-7.2 mm, and 27.0+/-8.9 mm, respectively. The mean age of patients with non-neoplastic polyp, adenoma, and adenocarcinoma were 44.8+/-11.3, 49.9+/-12.5, and 60.8+/-9.6, respectively. Age, size of polyp, number of polyp, presence of diabetes, and presence of symptom showed statistically significant difference between the neoplastic polyp and non-neoplastic polyp groups. But only age, size of polyp, number of polyp were statistically independent factors associated with neoplastic polyp (p<0.05). To predict the neoplastic polyp, sensitivity was 94.4%, but specificity was 18.3% on the basis of 10 mm criteria. whereas sensitivity and specificity was 76.0% and 55.5% on the 12 mm-criteria. CONCLUSIONS: On the basis of our analysis, the size of polyp is the most important factor to predict the malignancy. In the 10 mm criteria, sensitivity is satisfactory but specificity is very low. Therefore 10 mm size should not be considered to be the absolute size-criterion for surgery.