Chemical states of Sm doped layered perovksite, SmBa1-xSrxCo2O5+d (x = 0 and 0.5), have been investigated by X-ray Photoelectron Spectroscopy (XPS). Substitution of Sr in SmBa1-xSrxCo2O5+d oxide system shifts the binding energy of Sm 3d(5/2) to the more positive side and the charge state of Sm remained Sm3+. Therefore, the substitution of Sr into the SmBa1-xSrxCo2O5+d oxide system does not change the charge state of Sm. Three types of oxygen species were observed in SmBa0.5Sr0.5Co2O5+d (SBSCO) and SBCO from the O 1s spectra comprised of lattice oxygen, carbonated species and adsorbed oxygen species with respect to the measured binding energy ranges. The more Sr was substituted into the Sm doped layered perovskite, the larger the binding energy values became. In case of the Co spectra of SBSCO, two satellite peaks were observed at the range of 786.0-789.0 eV and at 804.93 eV. The evidence of Co3+ and Co4+ indicated that Co is existing in the chemical form of mixed valence state including Co3+ and Co4+ in SBCO and SBSCO oxide systems. (C) 2013 Elsevier B. V. All rights reserved.