Background:The aim of the present study is to assess the image quality of multislice and cone-beam computed tomography using water, plaster of paris, and motor oil (WPO) phantom. Methods: A test object (radiographic phantom) were constructed, made up of 3 aligned acrylic cylinders filled with: (1) Distilled water, (2) Bubble free plaster, and (3) Motor oil. Subsequently, the cylinder was scanned with CBCT and MSCT using 3 FOV sizes with the cylinder positioned in the center of the FOVs. Test is made using multislice CT and 3 machines CBCT Planmeca, Vatech and Neotome. Results In the present study, Neotome, Planmeca and Vatech showed high significant measurements than MSCT in Plaster of Paris and Motor oil. The results of this study showed an excellent correlation between the voxel values from CBCT and the Hounsfield units derived from MSCT. Conclusion:In assessing density using CBCT, the Y = 0.682 (x) -161 equation is therefore recommended.