Little attention has been focused on radical and diradical formations from compounds that contain both phenol and thiol groups. Computational studies were conducted on radicals and diradicals from mercapto- and bismercaptocatechols to provide insight into their relative stability. The loss of a hydrogen atom from mercapto- or bismercaptocatechol produces S- and O-centered radicals of similar energy. The loss of two hydrogen atoms from 3,4-bismercaptocatechol is an example where a number of quinone and diradical structures become possible. However, the energetics are consistent with a 4-membered ring disulfide (dithiete) playing an important role in the two electron oxidation reaction of 3,4-bismercaptocatechol.