The influence of electrode modification by Atomic Layer Deposition (ALD) of ceria (CeOx) and strontium oxide (SrO) on the performance of solid oxide fuel cell (SOFC) cathodes was examined. The cathodes were prepared by infiltration of nitrate salts into porous yttria-stabilized-zirconia (YSZ) scaffolds to form composites with 35-wt% La0.8Sr0.2FeO3 (LSF), La0.6Sr0.4CoO3 (LSCo), or Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF). Both CeOx and SrO films were found to be detrimental to cathode performance; however, the primary mechanism behind the deactivation was different. The SrO films were found to geometrically block the active electrode surface area, while CeOx films strongly deactivated the cathode in ways that could not be explained simply by physical blocking. Submonolayer coverages of CeOx significantly increased the impedance of LSF-YSZ electrodes, while LSCo-YSZ and BSCF-YSZ electrodes were affected to a much lesser extent. The results imply that oxides deposited by ALD affect the oxygen adsorption ability of the electrode, and demonstrate the importance of oxide morphology in attempts to promote the performance of perovskite-based electrodes. (C) 2013 The Electrochemical Society. All rights reserved.