Provided are a memory system, a method of reading data and a method of finding read thresholds. The method of finding read thresholds includes: selecting a channel distribution among a plurality of channel distributions that corresponds to a read page of the memory device to be read in response to a read command; generating a Trellis diagram based on a decoding scheme and a type of the read page; determining an optimal path through the Trellis diagram using the selected channel distribution according to a dynamic programming algorithm; and finding the read thresholds from the optimal path.