Nano-crystalline La0.5Sr0.5CoO3-x (LSCO) thin films with a thickness of similar to 400 nm were deposited on a polycrystalline CGO substrate using pulsed laser deposition. AC impedance measurements were performed on symmetric cells between 400-600 degrees C in 0.01 <= pO(2) <= 1 atm. The oxygen non-stoichiometry in LSCO thin films was obtained by utilizing a hypothetical cell where oxygen transport was limited by the surface exchange reaction. It was found that the oxygen non-stoichiometry was about one order of magnitude lower than that observed for bulk LSCO. At 600 degrees C, in air, the area specific resistance (ASR) of the LSCO thin film is about 0.06 ohm cm(2).