Molar compositions of carbon dioxide (and hydrogen) in the gas phase in equilibrium with gas hydrate and aqueous phases were measured for various (H-2 + CO2) gas mixtures + water systems in the temperature range of 273.6-281.2 K at pressures up to similar to 9 MPa. The compositions of the gas phase were measured using an isochoric technique, in combination with the ROLSI capillary gas-phase sampling and a gas chromatography technique. The compositional data generated in this work are compared with the literature data, and the agreement is found to be generally acceptable.