Methods and apparatus are disclosed for combining advertising messages with short message service (SMS) messages in a wireless communications system. A signaling message processing and routing node transmits and receives short message service (SMS) data packets via a communications network. The routing node includes an SMS message processing module that determines whether an SMS message should be modified to include advertisements. SMS messages, whether modified or left unmodified, are forwarded to a destination mobile communications device. The SMS message processing module applies rules to match selected advertisements with the SMS message. The determination of whether to modify the SMS message to include a selected advertisement is based on a variety of considerations including: the content and format of the SMS message; the content and format of the advertisements; the communications and display characteristics of the destination mobile communications device; and the limitations of the channel used to communicate the message to the destination mobile communications device.