A method of controlling a dimming operation of an organic light emitting display device that includes an organic light emitting element, a first transistor connected to a data line and a gate line, and a second transistor connected to the first transistor and the organic light emitting element, is provided. By the method, image data is compensated using a plurality of look-up tables respectively corresponding to a plurality of dimming modes, to be outputted compensation data. The compensation data are converted to a data voltage to be provided the organic light emitting element with the data voltage. A level of a current applied to the organic light emitting element is adjusted according to the dimming.