The crystalline solvates containing fullerenes and (di)methylnaphthalenes were investigated by thermal analyses and X-ray diffraction methods. It was found that C-60 With (di)methylnaphthalenes forms two types of stable solvates: either at the molar ratio 1:2 decomposing at temperatures close to 100 degrees C or at 1:1 molar ratio decomposing in the temperature range 120-224 degrees C. Crystalline lattice and thermal stability of the solvates depends on the structure of the solvent molecules. The strong solute-solvent interaction is also manifested by the modification of the C-60 absorption spectra in solution. The results are discussed using semiempirical quantum chemistry methods.