A theoretical analysis of modified chemical vapor deposition (MCVD) of solid oxides in porous media for ceramic membrane preparation and/or modification is presented in this paper. Semi-analytical solutions have been obtained to describe the evolution of solid deposit profiles inside porous substrates, using a phenomenological model that takes into account intrapore precursor diffusion, chemical reaction and pore geometry change. Explicit equations have been derived which correlate the three main deposition characteristics, deposit location, deposit zone thickness and pore closure time to the CVD experimental parameters and substrate pore structure. Such explicit equations provide better insight into this unique CVD process for advanced materials synthesis and are very useful in practical applications. A comparison of the semi-analytical solutions with a numerical solution based on the finite element method is also presented. The semi-analytical solutions are in good agreement with the numerical solutions, especially under the conditions used for ceramic membrane preparation and/or modification.