The present dental reconstructed computed tomography (CT) images consist of continuously piled-up axial CT images that are perpendicular to the axial CT plane. In the mandibular posterior region, the angles of designed implants frequently differ from the angles perpendicular to the axial CT plane and the measurement of mandibular height is inaccurate. This study was performed to clarify the measurement accuracy of double-oblique reconstructed images in multi-slice helical CT, using dried mandibles. The mandibular height was measured from the alveolar crest immediately below the aluminum tube to the superior border of the mandibular canal using the double-oblique reconstructed images and the micro-CT average images of three semi-lateral dried mandibles. The mean of the differences between the double-oblique reconstructed images with a table pitch of 1.5 in a helical scan and the micro-CT average images was 0.31 mm. It is concluded that the accuracy of the double-oblique reconstructed image measurements with helical scan is high. So this double-oblique program can be applied to the imaging diagnosis in dental implant treatment.