A group contribution (GC) method combined with a SAFT equation of state (EOS) [Tamouza et al., Fluid Phase Equilib. 2004, 222 − 223, 67 and 2005, 228 − 229, 409] is extended here to model vapor−liquid phase equilibria of binary mixtures of H2 + n-alkanes and CO2 + n-alkanes. Modeling these systems requires binary interaction parameters k ij that are estimated here in the same spirit as pure compound GC−SAFT parameters, i.e., through a specific group contribution method. Molecule−group interaction parameters (k H 2 ,CH 2 , k H 2 ,CH 3 , k CO 2 ,CH 2 , and k CO 2 ,CH 3 ) are used rather than molecule−molecule interaction parameters. Two versions of SAFT are tested here:  the Perturbed-Chain SAFT (PC−SAFT) [Gross and Sadowski, Ind. Eng. Chem. Res. 2000, 40, 1244] and Variable-Range SAFT (VR−SAFT) [Gil-Villegas et al., J. Chem. Phys. 1997, 106, 4168]. The results are very encouraging, particularly for predicting binary mixtures of CO2 and heavy n-alkanes. Mixtures that contain H2 are modeled here with deviations that compare well with those of the classically used Grayson−Streed model.