An OLED display device includes display panel and a panel driver. The panel driver receives input image data at an input frame frequency and determines whether the input image data represent a still image. When the input image data do not represent the still image, the panel driver drives the display panel at a first output frame frequency substantially equal to the input frame frequency. When the input image data represent the still image, the panel driver drives the display panel at a second output frame frequency lower than the input frame frequency for a low frequency driving time and drives the display panel at a third output frame frequency higher than the second output frame frequency for a high frequency insertion time determined by one of a panel characteristic of the display panel and a representative gray level of the input image data, after the low frequency driving time.