A method and apparatus can diagnose a cell defect of a PDP module. The method can include dividing a screen of a PDP module into a plurality of regions, displaying a pattern for diagnosing the cell defect on less than all the regions, and blocking at least one of the remaining regions. Further, determined cell defects identified in at least two of the plurality of regions have different weights when combined to determine a resulting value for comparison to a threshold for the PDP module.