An OLED display device includes a display panel including first and second partial panel regions, a scan driver configured to sequentially apply scan signals to the first and second partial panel regions in a normal driving mode, and to sequentially apply the scan signals to a driven one of the first and second partial panel regions in a partial driving mode, and a data driver configured to apply data signals to the first and second partial panel regions in the normal driving mode, and to apply the data signals to the driven one of the first and second partial panel regions in the partial driving mode. In the partial driving mode, the scan driver is configured to sequentially apply diode initialization signals to the driven one of the first and second partial panel regions, and to concurrently apply the diode initialization signals to a non-driven one of the first and second partial panel regions.