The effect of pressure on carbon dioxide solubility in water is significantly smaller than that of temperature under hydrate-liquid water (H-L-w) equilibrium As a result, experimental values of carbon dioxide solubility in the water rich liquid phase under H-L-w equilibrium are often inconclusive and in some cases contradictory This work proposes a theoretical derivation, based on fundamental thermodynamics, of the gas hydrate former solubility dependency on pressure for any binary system under two-phase equilibrium The obtained expression is applied to the carbon dioxide-water system under both hydrate-liquid water and vapour-liquid water equilibrium It is shown that the solubility of carbon dioxide in the water rich liquid phase increases with increasing pressure under H-L-w equilibrium The predicted trend is then compared to the limited experimental data available in the literature