In an organic light emitting display, a conductive layer is formed on the bottom surface of a substrate, and the conductive layer is used as a wiring line for supplying a power source, and as the electrode of a capacitor. Therefore, it is possible to easily secure the aperture ratio of a pixel, to easily solve the problem of IR drops by controlling the area or thickness of the conductive layer, and to easily secure the electrostatic capacity of the capacitor. In particular, in the case of a front surface light emitting structure, since a capacitor of a metal/insulating layer/metal (MIM) structure may be formed in a light emitting region, enough aperture ratio and electrostatic capacity may be secured. Therefore, a high resolution organic light emitting display may be easily realized, and enough aperture ratio and electrostatic capacity are secured so as to realize high picture quality.