A semiconductor memory device includes a memory cell array, a control logic circuit, an internal processing circuit, and an error correction circuit. The control logic circuit generates an internal processing mode signal in response to a command from a memory controller. The internal processing circuit selectively performs the internal processing operation on a first set of data read from the memory cell array to output a processing result data, in response to the internal processing mode signal. The error correction circuit performs an error correction code (ECC) encoding on the processing result data to generate a second parity data and stores the processing result data and the second parity data in the memory cell array. The error correction circuit generates the second parity data by selecting the same ECC of a plurality of ECCs as a first ECC.