With the recent growing interest in flexible electronics, many studies are being conducted on flexible transparent conducting electrodes (TCE) such as Ag nanowires, Ag nanomeshes, carbon nanotubes, and graphenes. However, it will take time for such technologies to replace Sn-doped In2O3 (ITO), which is now widely used, due to challenges with reliability, mass-production, cost, and industry infrastructure. In this study, ITO films with different thicknesses were deposited on a flexible polymer substrate to investigate their optical and electrical properties and flexibility as a function of film thickness. Regardless of thickness, the ITO films' transmittance was about 80% at similar to 550 nm wavelength. The sheet resistances of all films were below 100 Omega/sq although resistance increased with decreasing film thickness. As a result of bending tests, it was found that thinner films had a higher threshold against bending strain. The sheet resistances did not significantly change above a bending radius of similar to 5 mm. In particular, the 50 nm-thick ITO film endured to a bending radius of similar to 3mm, showing that it is a viable transparent electrode for flexible optoelectronics. (C) 2016 Elsevier B.V. All rights reserved.