In the present study, we investigated the reduction and the evolution of oxygen from lithium containing DMSO based electrolytes at gold. The number of electrons that are transferred per O2 (z-value) during oxygen reduction depends on the structure of the electrode: Despite the presence of Li+, O2 is reduced electrochemically to superoxide at smooth gold electrodes and at low overpotentials. At porous electrodes a z-value close to 2 e−/O2 indicates Li2O2-formation even at low overpotentials. This is ascribed to a reaction of superoxide, which is catalyzed by gold-particles at open circuit. This behavior is also responsible for the non-proportionality between reduced and evolved amounts of oxygen. Furthermore, we observed a linear relationship between evolved amounts of CO2 and reduced amounts of oxygen, indicative for electrolyte decomposition during oxygen reduction. Combined electrochemical quartz crystal microbalance (eQCMB) and Differential electrochemical mass spectroscopy (DEMS) measurements reveal that mass changes that occur in the anodic sweep are due to the evolution of CO2, whereas oxygen evolution takes place without any mass changes. The observed m.p.e-values (mass changes per transferred electron) are affected by convection due to the formation of soluble reduction products which observed in rotating ring disc electrode measurements.