In order to investigate the effect of Sr composition on performance of La1-xSrxCoO3-delta (LSC) cathodes, LSC thin-film cathodes which have different Sr doping levels as x = 0.2 (LSC82) and x = 0.4 (LSC64) are selected and fabricated by using pulsed laser deposition (PLD). The cathodes are formed on an anode-supported solid oxide fuel cell (SOFC) with an yttria-stabilized zirconia (YSZ) electrolyte and a gadolinia-doped ceria (GDC) buffer layer. The power output of the cell with the LSC64 cathode (LSC64 cell) is at least twice higher than that of the cell with the LSC82 cathode (LSC82 cell) at operating temperatures below 650 degrees C. Since microstructural differences are hardly found between the two thin-film cathodes, this performance difference is believed to originate from the difference in the defect chemical nature of LSCs and its related electrocatalytic activity. In terms of the performance drop by decreasing the operation temperature or the oxygen partial pressure at the cathode side, that of the LSC64 cell is much less than that of the LSC82 cell as well. (C) 2012 The Electrochemical Society. [DOI: 10.1149/ 2.038210jes] All rights reserved.