This paper reports the four-phase (ice + hydrate + CO_2 + 3,3-dimethyl-2-butanone) equilibrium pressure-temperature conditions at temperatures (252 to 272) K in the system of water, CO_2 and 3,3-dimethyl-2-butanone. The pressure range of the present measurements in the system is (0.44 to 1.04) MPa. This paper also reports the four-phase (ice + hydrate + CO_2 + 2,2-dimethylbutane) equilibrium pressure-temperature conditions at temperatures (254 to 263) K in the system of water, CO_2 and 2,2-dimethylbutane. The pressure range of the present measurements in the system is (0.49 to 0.74) MPa. The measurements were carried out using isochoric methods. The results indicate that structure H hydrate formed with CO_2 and 3,3-dimethyl-2-butanone is stable exclusively at the temperatures below 272 K.