A digital broadcasting system and a data processing method are disclosed. A receiving system of the digital broadcasting system comprises a baseband processor, a management processor and a presentation processor. The baseband processor receives a broadcast signal including mobile service data and main service data, wherein the mobile service data configure a Reed-Solomon (RS) frame. The RS frame includes at least one of the mobile service data and notification messages. The notification messages are packetized in accordance with any one of a first transport protocol and a second transport protocol. The management processor decodes the notification messages from the RS frame in accordance with any one of the first transport protocol and the second transport protocol. The presentation processor directly outputs the decoded notification messages to an output unit in accordance with a channel which transmits the decoded notification messages, or outputs the decoded notification messages to the output unit only if a user selects the notification messages.