The co-adsorption of sodium dodecyl sulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS), on the 1-decanethiol self-assembled monolayer (SAM)-functionalized polycrystalline gold surface, is investigated by electrochemical techniques. The peak current (cyclic voltammetry) and charge transfer resistance (impedance spectra) variations are measured, concerning the [Fe(CN)(6)](3-)/[Fe(CN)(6)](4-) couple redox process. SDBS is found to yield a more efficient inhibiting barrier (towards the charge transfer process), when compared to the SDS one. Thus, it is suggesting that a higher tendency of SDBS to be co-adsorbed within the 1-decanethiol SAM with respect to SDS.