An organic light emitting display includes a scan driver for driving scan lines and emission control lines, a data driver for driving data lines, a display unit including pixels at crossing regions of scan lines and data lines, first power source lines coupled to a first power source configured to supply a first voltage and coupled to pixels in columns, horizontal power source lines extending in a direction parallel with scan lines and coupled to pixels in rows, and a second power source line coupled to the horizontal power source lines and to a second power source configured to supply the same voltage as the first power source, each of the pixels being configured to store a voltage corresponding to voltages of the second power source and a data signal and to control an amount of current that flows from the first power source in accordance with the stored voltage.