A digital television transmitting system includes a pre-processor, a packet generator, an RS encoder, and a trellis encoder. The pre-processor pre-processes enhanced data by coding the enhanced data for first forward error correction (FEC) and expanding the FEC-coded enhanced data. The packet generator generates first and second enhanced data packets including the pre-processed enhanced data and main data packets and multiplexes the enhanced and main data packets. The first enhanced data packet includes an adaptation field including the pre-processed enhanced data and second enhanced data packet includes a payload region including the pre-processed enhanced data. The RS encoder performs RS encoding on the multiplexed data packets for second forward error correction (FEC), and the trellis encoder performs trellis encoding on the RS-coded data packets.