The absorption rate of SO2 into calcium sulfite slurries is predicted by means of a model, based on the film theory, which considers absorption in a liquid film located at the gas-liquid interface and simultaneous dissolution of calcium sulfite in a liquid film surrounding the particles. The involved reactions are supposed to be reversible and instantaneous. Diffusive transport of ionic and molecular species in both films accounts for the effect of equilibrium and, due to unequal diffusivities of ions, for the effect of the electric potential gradient. The Nernst theory of stagnant film is therefore applied. Predicted overall gas mass transfer coefficients and mean absorption rates were found to be in good agreement with experimental values obtained at different conditions in a cable contactor.