An organic light-emitting diode display and a method of manufacturing the same are disclosed. In one aspect, the display includes a substrate including a display area configured to display an image and a peripheral area surrounding the display area. The display also includes a thin film transistor formed in the display area over the substrate, a first planarization layer covering the TFT in the display area, and an OLED formed over the first planarization layer and electrically connected to the TFT. The display also includes a second planarization layer formed in the peripheral area, the second planarization layer including a plurality of out-gassing holes formed therein, and at least a portion of the second planarization layer thinner than the first planarization layer.