An organic light emitting diode (OLED) display includes a scan line, a data line, a driving voltage line, a switching transistor, a driving transistor and an OLED. The scan line is formed on a substrate to transmit a scan signal. The data line and the driving voltage line, intersecting the scan line, transmit a data signal and a driving voltage, respectively. The switching transistor, electrically coupled to the scan line and the data line, includes a switching semiconductor layer, a switching gate electrode, and a gate insulating layer having a first thickness. The driving transistor, electrically coupled to the switching drain electrode, includes a driving semiconductor layer, a driving gate electrode and a gate insulating layer having a second thickness. The OLED is electrically coupled to the driving drain electrode. The data line and the driving voltage line are formed with different layers from each other.