An organic light emitting display device, comprising: a plurality of scan lines (S1 to Sn) and a plurality of data lines (D1 to Dm); a scan driver progressively supplying scan signals to the scan lines (S1 to Sn); a data driver having a plurality of output lines (O1 to Om/i) and supplying data signals to the output lines (O1 to Om/i) of the data driver during a period in which the scan signals are supplied; and a demultiplexer unit including a plurality of demultiplexers, each demultiplexer being coupled to a respective one of the output lines (O1 to Om/i) of the data driver, and supplying the data signals to a respective set of i data lines (D1 to Di), wherein i is a natural number ≥ 2, each demultiplexer including: i first switches, each first switch being coupled between said output line (O1 to Om/i) of the data driver and a corresponding data line among said set of data lines (D1 to Di), and [i-1] second switches, each second switch being coupled between a first initialization power source providing a first initialization voltage (Vint1) and a data line (D2 to Di) except a first data line among said set of data lines (D1 to Di), wherein the first data line is the data line to which a data signal is supplied first among the set of data lines (D1 to Di); wherein each of the second switches is turned on by the same control signal that turns on the first switch coupled to the first data line, so that the initialization voltage (Vint1) is supplied to the data lines (D2 to Di) of said set of data lines (D1 to Di) except the first data line when the data voltage is supplied to the first data line, and characterized in that a control signal supplied to the first switch coupled to the first data line has a first width wider than a second width of a control signal (CS2, CS3) supplied to the first switch coupled to the data line (D2 to Di) except the first data line among the set of data lines (D1 to Di), wherein, before each of the scan signals is supplied to the a respective one of the scan lines (S1 to Sn), the first data signal corresponding to each horizontal period is supplied to the first data line, and the voltage of the first initialization power source (Vint1) is supplied to the data lines (D2 to Di) except the first data line. a plurality of scan lines (S1 to Sn) and a plurality of data lines (D1 to Dm); a scan driver progressively supplying scan signals to the scan lines (S1 to Sn); a data driver having a plurality of output lines (O1 to Om/i) and supplying data signals to the output lines (O1 to Om/i) of the data driver during a period in which the scan signals are supplied; and a demultiplexer unit including a plurality of demultiplexers, each demultiplexer being coupled to a respective one of the output lines (O1 to Om/i) of the data driver, and supplying the data signals to a respective set of i data lines (D1 to Di), wherein i is a natural number ≥ 2, each demultiplexer including: i first switches, each first switch being coupled between said output line (O1 to Om/i) of the data driver and a corresponding data line among said set of data lines (D1 to Di), and [i-1] second switches, each second switch being coupled between a first initialization power source providing a first initialization voltage (Vint1) and a data line (D2 to Di) except a first data line among said set of data lines (D1 to Di), wherein the first data line is the data line to which a data signal is supplied first among the set of data lines (D1 to Di); i first switches, each first switch being coupled between said output line (O1 to Om/i) of the data driver and a corresponding data line among said set of data lines (D1 to Di), and [i-1] second switches, each second switch being coupled between a first initialization power source providing a first initialization voltage (Vint1) and a data line (D2 to Di) except a first data line among said set of data lines (D1 to Di), wherein the first data line is the data line to which a data signal is supplied first among the set of data lines (D1 to Di); wherein each of the second switches is turned on by the same control signal that turns on the first switch coupled to the first data line, so that the initialization voltage (Vint1) is supplied to the data lines (D2 to Di) of said set of data lines (D1 to Di) except the first data line when the data voltage is supplied to the first data line, and characterized in that a control signal supplied to the first switch coupled to the first data line has a first width wider than a second width of a control signal (CS2, CS3) supplied to the first switch coupled to the data line (D2 to Di) except the first data line among the set of data lines (D1 to Di), wherein, before each of the scan signals is supplied to the a respective one of the scan lines (S1 to Sn), the first data signal corresponding to each horizontal period is supplied to the first data line, and the voltage of the first initialization power source (Vint1) is supplied to the data lines (D2 to Di) except the first data line.