In this work, the potential of low-viscous branched polymers for gas separation applications such as CO2 absorption from flue gas is examined. Carbon dioxide and nitrogen solubilities are measured at low pressures for linear and branched polyethers, hyperbranched polyesters, and polyamines such as a polyamidoamine and a polyethylene imine as well as in their aqueous solutions. The results are reported in terms of Henry constants in the temperature range T = 310-370 K. The densities of the pure polymers and their aqueous solutions are measured between T = 293.15 and 363.15 K. The selectivities of the polymers for CO2/N-2 and the enthalpies of absorption at infinite dilution are determined. The group-contribution method UNIFAC-FV is applied to the CO2 solubilities in polyethers and the hyperbranched polyester. It has been shown that branched polymers are promising candidates for gas absorbents with a high capacity for CO2 and with large selectivities. The UNIFAC-FV model is able to predict the CO2 solubilities in the investigated polymers.