The temperature-concentration phase diagrams as well as the structure and the morphology of ternary systems sPS/solvent 1/solvent 2, where sPS is syndiotactic polystyrene, solvent I is naphthalene, and solvent 2 is either benzene or biphenyl, are reported. The binary solvents have been chosen for two reasons: (i) They usually produce different molecular compound forms in binary systems: sPS/naphthalene gives clathrate compounds (delta(c) form) and sPS/biphenyl forms intercalate compounds (delta(i) form), while in case of sPS/benzene both forms occur depending on temperature and concentration. (ii) The binary solvent Mixtures form themselves molecular compounds. The main outcomes of this investigation are threefold: (i) existence of ternary compounds, (ii) possibly another new Compound form, and (iii) intercalates are still formed for low content of naphthalene in sPS/naphthalene/benzene systems, while they no longer occur in sPS/naphthalene/biphenyl systems.