A display device including: a display panel; and a signal controller which controls signals for driving the display panel, where the signal controller includes a representative value generator which sequentially operates a portion of image data of one frame, where the representative value generator moves a last position digit into another position digit of the portion of the image data and generates a representative value representing a portion of a frame image corresponding to the portion of the image data; a storage portion which stores the representative value therein; and a comparator which compares the representative values of present and prior frames to determine whether the portion of the frame image is a still image or a motion picture, and the signal controller controls the signals for driving the display panel such that a driving frequency for the still image is lower than a driving frequency for the motion picture.