OBJECTIVES: This study aimed to measure the volume of the third cervical vertebra using head and neck multi-detector computed tomography (MDCT) and establish a sex determination model based on sex differences in volume. METHODS: Head and neck CT images of 85 patients were obtained for dental diagnostic and therapeutic purposes. Digital Imaging and Communications in Medicine (DICOM) data obtained from head and neck CT were constructed using a three-dimensional image analysis software. A region of interest was created that included the entire third cervical vertebra and its volume was measured. Descriptive statistics were calculated for the measurements, and the means, standard deviations, and medians of the measurements were calculated separately for men and women. To create a sex determination model, binomial logistic regression analysis was performed using the training data group, with vertebral volume and sex as the explanatory and objective variables, respectively. RESULTS: The mean score of men was significantly higher than that of women. The sex determination model using the volume of the third cervical vertebral body resulted in an 80% correct sex classification rate. CONCLUSION: The sex determination model can be used with other regional methods to aid sex determination.