An organic light emitting diode display device comprising: a display panel configured with pixels which each include an organic light emitting diode (OLED) and a driving transistor applying a driving current to the organic light emitting diode (OLED), and with reference voltage supply lines connected to the pixels; a gate driver connected to the pixels through gate lines; a data driver configured to apply a sensing voltage to the pixels through data lines in a sensing mode and enable a sensing current to flow through each of the driving transistors; a sensing driver configured to detect threshold voltages by sensing voltage information opposite to the driving currents which flow through the driving transistors using the reference voltage supply lines; and a brightness compensation circuit configured to derive negatively shifted degrees of threshold voltages of the driving transistors from the sensed threshold voltages, detect a bright-defected pixel on the basis of the negatively shifted degrees, and generate a compensation gray value for the bright-defected pixel wherein the brightness compensation circuit includes: a comparator configured to derive the negatively shifted degrees of the threshold voltages of the driving transistors from the sensed threshold voltages by comparing the sensed threshold voltages of a pixel and adjacent pixels thereto with one another; a bright spot detector configured to detect the bright-defected pixel on the basis of the negatively shifted degrees from the comparator; and a compensation value generator configured to derive the compensation gray value from an input gray value for the bright-defected pixel which is detected by the bright spot detector. a display panel configured with pixels which each include an organic light emitting diode (OLED) and a driving transistor applying a driving current to the organic light emitting diode (OLED), and with reference voltage supply lines connected to the pixels; a gate driver connected to the pixels through gate lines; a data driver configured to apply a sensing voltage to the pixels through data lines in a sensing mode and enable a sensing current to flow through each of the driving transistors; a sensing driver configured to detect threshold voltages by sensing voltage information opposite to the driving currents which flow through the driving transistors using the reference voltage supply lines; and a brightness compensation circuit configured to derive negatively shifted degrees of threshold voltages of the driving transistors from the sensed threshold voltages, detect a bright-defected pixel on the basis of the negatively shifted degrees, and generate a compensation gray value for the bright-defected pixel wherein the brightness compensation circuit includes: a comparator configured to derive the negatively shifted degrees of the threshold voltages of the driving transistors from the sensed threshold voltages by comparing the sensed threshold voltages of a pixel and adjacent pixels thereto with one another; a bright spot detector configured to detect the bright-defected pixel on the basis of the negatively shifted degrees from the comparator; and a compensation value generator configured to derive the compensation gray value from an input gray value for the bright-defected pixel which is detected by the bright spot detector. a comparator configured to derive the negatively shifted degrees of the threshold voltages of the driving transistors from the sensed threshold voltages by comparing the sensed threshold voltages of a pixel and adjacent pixels thereto with one another; a bright spot detector configured to detect the bright-defected pixel on the basis of the negatively shifted degrees from the comparator; and a compensation value generator configured to derive the compensation gray value from an input gray value for the bright-defected pixel which is detected by the bright spot detector.