Electron emission display device and driving method thereof

An electron emission display device and a driving method thereof are disclosed. The device and method limit a brightness thereof in order to reduce power consumption, and adjust a gamma compensation according to a limit width of the brightness to reduce a gamma compensation deviation, causing an increase in a quality of an image. In a pixel portion, a brightness is controlled corresponding to applied voltages of a first electrode and a second electrode and an emission time. An image signal summing section receives and sums image signals by frame periods. A gamma selector selects a gamma based on an output signal of the image signal summing section and compensates for the image signals. A data driver converts the compensated image signals to generate a data signal, and transfers the data signal to the first electrode. A scan driver generates and transfers a scan signal to the second electrode.