A method of processing a digital television (DTV) signal in a DTV receiver, the method including receiving a plurality of extended text table (ETT) instances appearing in transport stream packets with common PID values, the ETT instances having common table ID values, each ETT instance comprising a section header and a message body, the message body containing an extended text message (ETM) which provides detailed descriptions of a virtual channel or an event associated with each ETT instance, wherein the section header containing a table identification (ID) extension field that serves to establish uniqueness of each ETT instance, and the message body includes an ETM identifier to identify the ETM, the ETM identifier having source identification information specifying a programming source of a virtual channel associated with the each ETT instance, demodulating the digital television signal, and identifying at least one pertinent ETT instance from the plurality of ETT instances.