A semiconductor memory device includes a memory cell array, an error correction code (ECC) engine, a refresh control circuit, a scrubbing control circuit and a control logic circuit. The refresh control circuit generates refresh row addresses for refreshing a memory region on memory cell rows in response to a first command received from a memory controller. The scrubbing control circuit counts the refresh row addresses and generates a scrubbing address for performing a scrubbing operation on a first memory cell row of the memory cell rows whenever the scrubbing control circuit counts N refresh row addresses of the refresh row addresses. The ECC engine reads first data corresponding to a first codeword, from at least one sub-page in the first memory cell row, corrects at least one error bit in the first codeword and writes back the corrected first codeword in a corresponding memory location.