An extended version of the thermodynamic computation model for sorption isotherms and capillary condensation is introduced. With the combination of the excess surface work (ESW) and disjoining pressure approach sorption isotherms for various pore size distributions of cylindrical and slit-like mesopores are successfully modeled. The main idea is that during adsorption on pore walls the approaching films will collapse and capillary condensation proceeds, while evaporation is described with a modified Kelvin equation. In both cases adsorption and desorption, the surface tension dependency on the pore size is considered.