Recently; since various wireless communication services such as die PDC. the PHS, and the wireless LAN are provided, it is required to make a mobile terminal to handle several wireless communication services. Generally, these services operate at different frequencies with different polarization and radiation characteristics. Therefore, it is necessary to design a multi-mode antenna which- has multi-frequency band and different polarization and radiation pattern at each band, and the switching of the resonant modes should be controlled electronically.Many researches have been and are being performed 011 the multi-band antennas for this demand [l]-, and most of the antennas reported usually consist of parasitic elements for multi-resonance. However, the technique using the parasitic structures has some limitations because the design of the parasitic structure for multi-mode is very difficult. Recently, a reconfigurable leaky mode/patch antenna controlled by PIN diode switches has been reported , In this research, a dual-mode patch antenna is proposed where a PIN diode switch is used to change the resonant mode of the antenna. The characteristics of the antenna, such as the resonant frequency, radiation pattern, and the radiation efficiency are investigated experimentally and numerically.