Gas hydrates from a (40/60 mol %) CO2/H-2 mixture, and from a (38.2/59.2/2.6 mol %) CO2/H-2/C3H8 mixture, were synthesized using ice powder. The gas uptake curves were determined from pressure drop measurements and samples were analyzed using spectroscopic techniques to identify the structure and determine the cage occupancies. Powder X-ray diffraction (PXRD) analysis at -110 degrees C was used to determine the crystal structure. From the PXRD measurement it was found that the CO2/H-2 hydrate is structure I and shows a self-preservation behavior similar to that of CO2 hydrate. The ternary gas mixture was found to form pure structure II hydrate at 3.8 MPa. We have applied attenuated total reflection infrared spectroscopic analysis to measure the CO2 distribution over the large and small cavities. H-1 MAS NMR and Raman were used to follow H-2 enclathration in the small cages of structure I, as well as structure II hydrate. (C) 2009 American Institute of Chemical Engineers AIChE J, 55: 1584-1594, 2009