Semiconductor memory devices and methods of operating semiconductor memory devices

A semiconductor memory device includes a memory cell array, an error correction code (ECC) circuit, a fault address register, a scrubbing control circuit and a control logic circuit. The memory cell array includes memory cell rows. The scrubbing control circuit generates scrubbing addresses based on refresh operations performed on the memory cell array. The control logic circuit controls the ECC circuit such that the ECC circuit performs an error detection operation on a plurality of sub-pages in a first memory cell row to count a number of error occurrences, and determines whether to correct a codeword in which an error is detected based on the number of error occurrences. An uncorrected or corrected codeword is written back, and a row address of the first memory cell row may be stored in the fault address register as a row fault address based on the number of error occurrences.