Abstract: A flat panel display sequentially supplying data signals to a pixel portion using a demultiplexer and a method of driving the flat panel sufficiently supply scan signals in a horizontal period to prevent deformation and distortion of the data signal supplied to each pixel and compensate for a threshold voltage of a drive transistor of the pixel. The flat panel display includes a pixel portion having a plurality of pixels, a scan driver to supply scan signals to the pixel portion, a data driver to generate data signals, a dimultiplexer portion to sequentially supply the data signals to the pixel portion, and a lighting tester to supply a lighting test signal and an initialization signal to the pixel portion. Alternatively, the flat panel display includes a pixel portion having a plurality of pixels, a scan driver to supply scan signals to the pixel portion, a data driver to output data signals and a dimultiplexer portion to sequentially supply an initialization signal and the data signal to the pixel portion.