Polymer light emitting diodes (PLEDs) with ITO/PEDOT:PSS/PVK/PFO-poss/LiF/Al structure were prepared by spin coating method on the plasma-treated ITO(indium tin oxide)/glass substrates. PVK(N-vinylcabozole) and PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(styrene sulfolnate)] polymers were used as hole injection and transport materials. As blue light emitting material, PFO-poss(poly(9,9-dioctylfluorence) polymer was used. The dependence of the plasma treatment of ITO films on the optical and electrical properties of the PLEDs was investigated. The sheet resistance of ITO films increased slightly with increasing the plasma intensity from 20W to 300W in RF power. In contrast, the surface roughness was improved as the plasma intensity increased. The maximum current density and luminance were about 20 mA/cm2 and 250 cd/m2 at 9 V for the PLED sample coated on ITO/glass substrate with plasma treatment of 100W for 30s under 40 mtorr O2 pressure. The maximum emission spectrum of the PLEDs was 441 nm showing blue color.