This paper investigates the changes in the optical and discharge characteristics during the panel-aging process in ac plasma display panel as a parameter of the operating frequency. The resulting changes in the optical and discharge characteristics, including the firing voltage, dynamic voltage margin, three-dimensional IR emission, and SEM image, are then compared for the three different operating frequencies (10, 25, and 50kHz) during the panel-aging process. Our experimental results confirm that the 50kHz operating frequency is very effective in obtaining the uniform surface morphology of the MgO thin film during the panel-aging process.