The success of time-resolved imaging of an abnormal site embedded in thick tissue may rely on one's ability to quantify the absorption coefficient of the target as a specific spectroscopic signature. This task is particularly complicated when the scattering properties of the target differ from those of the surrounding tissue. Using data obtained from time- resolved transillumination experiments of abnormally absorbing and differentially scattering objects embedded in a tissue- like phantom, we show how a new deconvolution algorithm enables us to quantify the optical properties of the target. The algorithm is based on a photon random walk theory that expresses different time-dependent point spread functions to calculate the diffusive and absorptive contrasts obtained in time-of-flight measurements.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.