Background and purpose: Keratocystic odontogenic tumor is a locally aggressive developmental cystic neoplasm with high recurrence rate. In clinically, the differential diagnosis is important to appropriate treatment. The CT values for cystic contents are reflecting proportion of the component, and it can be information which supports imaging diagnosis. Proportion of the component for cystic contents is influenced by pathological development of the cystic lesion. However, to our knowledge, there are only few reports investigating the relationship between CT values and histopathological features on keratocystic odontogenic tumor. The purpose of this study was to assess the correlation between CT values and microvessel density in keratocystic odontogenic tumor.Materials and methods: Following IRB approval, cystic contents CT values of 19 subjects with keratocystic odontogenic tumor were measured. All studies were performed on preoperative CT examinations between April 2006 and November 2011. Microvessel densities for all subjects were also measured on immunohistochemical staining slides with CD34 antibody. Statistical analysis of correlation between cystic contents CT values and microvessel density was carried out with Spearman rank correlation coefficient. The subjects were divided into two groups by the presence or absence of high-density area in the cystic lesion. The significant difference of microvessel density between those two groups was tested with Mann-Whitney U test.Results: Cystic contents CT values correlated with microvessel density of the lesions (r = 0.48, P = 0.036). Subjects with high-density spots in cystic contents had significantly higher microvessel density of the lesions (P < 0.05).Conclusions: Cystic contents CT value of keratocystic odontogenic tumor in the mandible was correlated with microvessel density. These results suggested that CT value may have information for lesion activity and potential of recurrence for keratocystic odontogenic tumor.