The solubility of hydrogen sulfide and carbon dioxide in N-octyl-2-pyrrolidone (NOP) was measured up to 1.4 MPa at 303 and 324 K using the static synthetic method. Experimental results were compared to those of the predictive Soave-Redlich-Kwong (PSRK) model, wherein the group interaction parameters for the NMP-group (N-methyl-2-pyrrolidone) were applied to the NOP systems. The reliability of the apparatus used and the applied data treatment were checked by comparing new experimental data for the system hydrogen sulfide + benzene at 304 and 324 K and pressures lip to 1.2 MPa, and for the system hydrogen sulfide + methanol at 298 K and up to 0.4 MPa, with published data measured with the analytical method.