The present paper reports isothermal three-phase equilibria (hydrate + aqueous + gas phases) for the carbon dioxide (CO(2)) + ethane (C(2)H(6)) mixed-gas hydrate system at (274.15, 279.15, and 284.15) K and the carbon dioxide (CO(2)) + tetrafluoromethane (CF(4)) mixed-gas hydrate system at (274.15 and 279.15) K. None of the equilibrium pressure composition curves of hydrate, aqueous, and gas phases shows discontinuity in the gradient. Both CO(2) + C(2)H(6) and CO(2) + CF(4) mixed-gas hydrates are the structure-I hydrate under the present experimental conditions, which is supported by the results of in situ Raman spectroscopy.