An organic light emitting display device and a driving method for the same is provided. The device includes a pixel portion adapted to receive a scan signal and a data signal and display an image. A scan driver generates and applies the scan signal to the pixel portion. A data driver generates and applies the data signal and a pixel voltage to the pixel portion. When the device is operating in the normal mode, the data driver also applies a drive voltage to a photo sensor also included in the display device. The photo sensor adjusts a luminance of the pixel portion according to a sensed brightness of ambient light. When the device is operating in the power saving or stand-by mode, the data driver controls the drive voltage off and thereby prevents power consumption by the photo sensor.