The use of X-ray computerized tomography scanning with a new dual-scan technique to measure porosity that is suitable for nondestructive characterization of cores, which are the main sources of data for reservoir characterization, is investigated. Scanning experiments to measure the porosity of a Berea sandstone core as well as a full-size limestone core are performed to compare conventional techniques with the proposed method. It has been found that the proposed method is faster and more accurate. The method is also nondestructive in nature, unlike the conventional laboratory and accepted standard method for computerized tomography scanning.