Water vapor diffusion and partition coefficients in cement slabs were determined by solving the inverse problem of one-dimensional unsteady mass diffusion based on measurements of the concentration of water vapor in a field and laboratory emission cell (FLEC) system. A solution for multi-process mass diffusion was obtained to analyze the influence of the non-uniform initial water vapor concentration distribution on the determination of diffusion and partition coefficients. The main factors affecting the accuracy of the diffusion and partition coefficients were discussed. Good agreement between the measured data and the predictions of the inverse problems showed that the mass diffusion in the cement slabs could be described accurately by the one-dimensional model. (C) 2003 Elsevier Ltd. All rights reserved.