This study is focused on the influence of impurities and electrode morphology on cyclic voltammograms (CV) of one of the most prominent solid state electrode systems, Pt(O-2)vertical bar YSZ, exemplifying the difficulties in unequivocal interpretation of CV in the solid state in general. By investigating differently prepared electrodes-either by Pt paste or pulsed laser deposition (PLD)-with and without an Si containing additive, the impact of both effects can be separated. For characterisation of the sample SEM, XRD, EDX, Tof-SIMS, XPS, and XPEEM have been used. We demonstrate that the presence of impurities can change the shape of CV and even cause peaks, a fact which has not been considered so far. The processes which theoretically can cause a CV peak in the electrode system Pt(O-2)vertical bar YSZ are discussed. We reconsider the information unambiguously obtainable from CV studies, and we comment on the controversial questions of the formation of interface Pt oxide and the appearance of spillover oxygen in CV studies. A compact commented survey of literature on CV studies of the system Pt(O-2)vertical bar YSZ is given. (c) 2009 Elsevier B.V. All rights reserved.