Abstract The reversible redox, hydrodesulfurization, and anodic oxidation of chemisorbed 2,5-dihydroxythiophenol (DHTP) and pentafluorothiophenol (PFT) have been compared at smooth polycrystalline gold and platinum thin-layer electrodes. The packing density and the mode of binding (through the -SH moiety) of the subject compounds were found to be identical on both surfaces. The width of the quinone/diphenol redox peak of the pendant hydroquinone group in DHTP was twice as large on platinum as it was on gold, indicating substantial substrate-mediated adsorbate-adsorbate interactions on the former surface. The extent of DHTP hydrodesulfurization (cleavage of the C-S bond with or without impairment of the pendant aromatic ring) was an order of magnitude lower on Au than on Pt. but the extent of anodic oxidation was only slightly lower on gold. PFT was readily and quantitatively desulfurized on Pt but not on Au, even at potentials negative of the hydrogen evolution reaction; on the other hand, oxidative removal of PFT at potentials below that for oxygen evolution occurred on Au but not on Pt.