The quenching of anthracene, perylene, 9-cyanoanthracene (9CA), and 9,10-diphenylanthracene (DPA) excited singlet states by carbon tetrabromide (CBr4) in supercritical CO2 has been studied systematically by use of the time-resolved fluorescence method. For 9CA-CBr4 and DPA-CBr4, there is enhanced fluorescence quenching at near-critical CO2 densities. On the other hand, the CO2 density dependence of fluorescence quenching in the anthracene-CBr4 and perylene-CBr4 systems follows the prediction of the hydrodynamic Smoluchowski equation for diffusion-controlled reactions. The results show, for the first time, that the enhancement in bimolecular fluorescence quenching reactions due to effects of local quencher concentration augmentation in supercritical CO2 is in fact system dependent.