A system and method for performing handover in a wireless mobile communication system are provided. In a Mobile Station, MS, -initiated scanning method of an MS in a wireless mobile communication system having at least two frequency bands with different central frequencies, the MS receives from a serving Base Station, BS, a mobile neighbor advertisement message including information about available radio resources of the neighbor BSs, transmits a new scanning request message to the serving BS, if the MS determines to measure Carrier-to-Interference and Noise Ratios, CINRs, of pilot signals from the serving BS and the neighbor BS, receives from the serving BS a response message for the scanning request message, including information about a BS which has reserved radio resources for a predetermined one of the at least two frequency bands, and measures the CINRs of the pilot signals in the predetermined frequency band.