The Polarizable Continuum Model has been used to study the effect of polymer matrix on Li (+) and Mg (2+) complexation in poly(ethylene oxide)-based solid electrolyte. Structures of complexes, stabilization energies, and vibrational frequencies are compared with corresponding vacuum values. The solvent effect of the polymer decreases with increasing cation coordination number. Optimized complex geometries do not differ significantly compared to vacuum calculations. Calculated shifts in vibrational frequencies depend on the complex structure; for hexacoordinated ion most frequencies are slightly red-shifted. The most important effect is the decrease of differences between relative stabilities of different structures in the solvent.