A digital broadcast transmitter and a method of processing a DTV signal in the digital broadcast transmitter are disclosed. The digital broadcast transmitter includes a pre-processor, a first multiplexer, a post-processor, and a second multiplexer. The pre-processor includes a first interleaver, a group formatter, and a packer formatter. The first interleaver interleaves symbols corresponding to mobile service data. The group formatter maps data corresponding to the interleaved symbols into at least one region of a data group and adds place holders for main service data and non-systematic RS parity data to the data group. The packet formatter removes the place holders for the main service data and the non-systematic RS parity data, and generates mobile service data packets having data in the data group in which the place holders for the main service data and the non-systematic RS parity data are removed.