Imaging using CT Scan utilizes the nature of the material that can absorb X-rays so the intensity of X-rays that penetrate the material will be attenuated. The attenuation coefficient of the material will provide information on the physical properties of it, in the image produced by CT Scan, the attenuation coefficients of the material is related to the number of Hounsfield Unit (HU). Alginate impression material is an irreversible hydrocolloid molding material that will form a gel when reacted with water without heating treatment process. The nature of alginate gel is elastic and has a fast setting time, often used in the manufacture of dentures. Alginate scanning using CT scan can provide information on alginate gel equivalents with human body tissue by comparing the HU values obtained. Alginate impression material that has been set up by using water is formed with a size of 11 x 11 cm with a thickness varying 5 mm, 7 mm and 9 mm and then scanned using CT Scan obtained an average HU of -51, which is equivalent to soft tissue such as lipid or breast.