An organic light emitting display can include a display panel including pixels, a degradation sensing circuit to sense a threshold voltage of organic light emitting diodes (OLEDs) in the pixels and calculate an average degradation value based on the sensed threshold voltage of the OLEDs, a compensation target adjustor to adjust a compensation target based on the average degradation value, when the average degradation value is reduced by a previously determined reference value, and a data modulator to add and subtract a luminance compensation value determined depending on the adjusted compensation target to and from input digital video data and modulate the input digital video data. Also, each time the average degradation value is reduced by the previously determined reference value, the compensation target adjustor reduces stepwise the compensation target in conformity with changes in the average degradation value, and a stepwise adjustment width of the compensation target is non-uniform.