Objective: The purpose of this study was to evaluate the accuracy of sex determination from the measurement of the area formed by 3 craniometric points related to the mastoid process i.e the porion, asterion, and mastoidale points in 3D reconstructed computed tomography of skull and comparison of its finding with the studies done by other authors where morphomertric analysis of mastoid process is done by manual method using vernier caliper or xerographic copies of skull or from CT Scan. Method: For the study, 200 3D reconstructed CT scan images of skull were analysed, 100 were males and 100 were females. The three craniometric points were marked to demarcate a triangle on both side of 3D skull and measurement was done by using Radiant Dicom software. Results: We observed that the mean of all mastoid parameters was more in male than in female. Even the surface area of mastoid process was higher in male than female. Results of present study compared with studies done by different workers in different regions. Each study showed that all the mastoid variables i.e distance from Porion to Mastoidale, Asterion to Mastoidale, Asterion to Porion and surface area of mastoid process were more in males than in females which correlates with our study. Conclusion: Knowledge of above dimensions of mastoid process and comparision of its findings with various methods of measurement increases the accuracy of sex determination.