The volatile compounds formed from the Maillard reaction in a model system treated with/without supercritical carbon dioxide (SC-CO2, 40 MPa, 140 °C) were investigated at three molar ratios (3:1, 1:1, and 1:3) of ribose to cysteine. The headspace volatiles generated in the reaction mixtures were examined by SPME in combination with GC'MS. The ratio of ribose to cysteine had complex effects on the volatiles formation and those effects got further complicated by the SC-CO2 treatment. The formation of thiols and polysulfur heterocyclic compounds was generally favoured at an equal molar ratio of reactants; disulfides were favoured at low ratio of ribose to cysteine; while the effect of reactant ratios on the formation of thiophenes and fused bicyclic compounds did not follow a consistent pattern. SC-CO2 treatment resulted in a reduction of most volatiles, however, promoted the formation of some well-known meaty aromatic compounds.