Computed tomography (CT) essentially assumes that rays such as X-rays propagate straight within the body ; therefore, it is difficult to apply this assumption to bodies which scatter the incident rays. Since the living tissues are very strong light-scattering media, realization of optical-CT scanners is not considered easy, although it is highly desired because of its possible ability to measure the oxygenation states in the body with a noninvasive method. This report shows how optical-CT imaging is possible by the use of time-resolved spectroscopy. The object is a cylindrical scattering medium containing a coaxial small cylinder with both scattering and absorption, while the reference is only the scattering cylinder. The light transmission data are generated by the Monte Carlo method. The temporal variations of the difference in the optical density between the object and reference provide the projection data necessary for the CT reconstruction procedure. The obtained image reflects the profile of the difference in the absorption coefficient between the object and the reference with satisfactory accuracy and spacial resolution.