The mastoid portion of the temporal bone has a variety of anatomical and physiological functions, including maintaining the balance of the middle ear pressure and protecting the inner ear. It has also attracted the interest of many investigators as a valuable tool in gender differentiation. In this study, we examined the mastoid measurements, volume and the degree of pneumatization in relation to age and gender. A cross-sectional study was conducted using computed tomography (CT) scans obtained from the radiology departments of the Military and Al Ragi Hospitals. Six measurements were taken from the mastoid process, the volume was calculated and the pneumatization was assessed on the axial plane at the level of the Sigmoid sinus, three parallel lines were drawn in relation to the sinus to classify the degree of pneumatization into four categories. The study exhibited that the average mastoid volume in the female was 7.14 mm3 and 6.62 mm3 on the right, and the left sides respectively, while in males it was 11.65 mm3 and 11.63 mm3 on the right and the left sides respectively. No significant bilateral differences in all measurements were observed in either males or females (P > 0.05), except for the oblique coronal diameter (OCD) in male, where a significant difference was found (P 0.05). A highly significant inverse association was found between age and the degree of pneumatization (P 0.05). CT scans was proved essential in evaluating the temporal bone’s pneumatization. The level of the pneumatization can be assessed by examining the air cells around the sigmoid sinus in axial CT images. Sexual dimorphism was observed in all mastoid process measurements. Keywords: Mastoid process, Pneumatization, CT Scan, Age, Gender.