A multi-mode mobile terminal in an idle state switches between a CDMA system mode and a WCDMA system mode. If the intensity of a WCDMA signal is maintained below a threshold value for longer than a predetermined period in a WCDMA idle state, the acquisition of the CDMA system is attempted, and a WCDMA modem is deactivated if the acquisition of the CDMA system mode was successful. Alternatively, the acquisition of the WCDMA system is attempted at regular intervals in a CDMA idle state, and a CDMA modem is deactivated if the acquisition of the WCDMA system was successful. At least any one of the two modes can be maintained in an activated state when a mode is switched into another mode so that the duration of an interruption of service can be minimized.