The electrochemically active surface area (ECSA) of metal-oxide supported platinum catalysts as obtained from hydrogen underpotential deposition (H-upd) and from carbon monoxide stripping experiments was investigated. It was demonstrated that both methods fail to give meaningful values of the ECSA if they are performed in the conventional way as known for pure Pt and carbon supported Pt catalysts, respectively. For both methods, the reason for this failure is the lack of a correct baseline for the integration of the associated charges. It was found that the cyclic voltammogram recorded in CO saturated electrolyte gives an improved baseline for the Hupd analysis. For CO stripping, a novel baseline method was developed by performing a "CO stripping simulation" (COSS) experiment in CO-free electrolyte. The first cycle of this COSS-experiment is an improved baseline for the integration of the CO stripping peak, since possible support reduction/oxidation currents can be accounted for. With these modifications, Hupd and CO stripping voltammetry can be used for metal-oxide supported platinum to yield true, reproducible and consistent values for the ECSA. (C) 2013 The Electrochemical Society. All rights reserved.