A portable data processing device with a data communication function is provided which includes an antenna, a receiver, a decoder, a RAM for storing a plurality of data items, and a CPU. The CPU retrieves, on the basis of identification data added to received data, associated data corresponding to the received data from among the data items stored in the RAM. The received data and the identification data are displayed on a display, and the associated data is then controlled to be displayed on the display in place of the received data. Accordingly, a message and other data relating to the contents of the message can be displayed by a simple input operation.