In a method of reading a memory device, difference information is generated based on a distance difference between a position of a read word-line and a position of a boundary word-line. The read word-line corresponds to a read address. The boundary word-line corresponds to a last programmed word-line in a memory block included in a memory cell array. A read word-line voltage and an adjacent word-line voltage are determined based on the difference information. The read word-line voltage is applied to the read word-line. The adjacent word-line voltage is applied to an adjacent word-line that is adjacent to the read word-line. A read data corresponding to the read address is outputted based on the read word-line voltage and the adjacent word-line voltage. The read method of the memory device according to example embodiments may be capable of increasing the performance by controlling the voltages applied to the adjacent word-line and the read word-line according to the difference information determined based on the read word-line and the boundary word-line.