Parylene was deposited on a bare polyethylene terephthalate (PET) and poly carbonate (PC) film surface to enhance the oxygen and water barrier properties at room temperature. The deposition rate of the parylene was observed to have increased linearly as the working pressure was increased. The oxygen plasma pre-treatment of the PET for the adhesion between bare film and parylene was mostly effective to 513, while the treatment of N-(2-Aminoethyl)-3-Aminopropylmethyldimethoxysilane solution at PC film resulted in 3B. Surface morphology and roughness were observed by atomic force microscopy and the barrier property was measured by oxygen transmission rate and water vapor permeation test equipments. The oxygen transmission rate (OTR) and water vapor transmission rate (WTR) of the PET film were reduced from 13.2 to 11.3 cc/m(2) day and from 4.6 to 2.0g/m(2) day, respectively. When the parylene layer was coated onto the PC film, however, the barrier effects were significant from out of detection limit to 53.9 cc/m(2) day for the OTR, and from 24.7 to 3.5g/m(2) day for the WTR. The real organic light emitting diode (OLED) device was fabricated with a parylene coated flexible substrate, which was subsequently deposited by transparent conducting layer and scratch-resistant layer. The initial brightness of the OLED device with a parylene buffer layer was 173 cd/cm(2), and 70% of its initial brightness was maintained after 40,000s. (c) 2006 Elsevier B.V. All rights reserved.