A liquid crystal display includes a pixel, an image signal modification unit and a data driver. The image signal modification unit includes a still image detection unit which receives a previous image signal and a current image signal of two consecutive frames and determines whether the current image signal is for a still image, a first modification unit which receives the current image signal and outputs a first current modified image signal or the current image signal, and a second modification unit which receives the current image signal and outputs a second current modified image signal or the current image signal. The data driver changes the second current modified image signal or the current image signal into a data voltage and supplies the data voltage to the pixel. The first modification unit outputs the current image signal when the current image signal is determined to be for the still image.