A parametric semi-empirical thermodynamic theory for the dissolution of glassy polymers in liquids is formulated based on the experimental results on Gibbs energy, enthalpy and entropy of mixing in isothermal conditions for a large number of systems. The values of these thermodynamic functions include the contribution from the glassy structure of the polymer, which depends on the volume fraction of metastable voids, the cohesion energy of polymer, and the entropy depression parameter. The glassy-state contribution to the enthalpy and entropy of mixing is large and negative, which provides sufficient difference from the same functions for the elastic polymers. However, this also leads to the enthalpy/entropy compensation, and the values of Gibbs energy of mixing only weakly depend on the glassy nature of the polymer. The theory is shown to provide adequate explanation for all specific features of the concentration dependences of different thermodynamic functions found in experiment at constant temperature. The parameters of the model are tabulated for a large variety of solutions of polymer glasses.