In this paper, a design of Fabry-Pérot Cavity antenna at millimiter-waves frequencies is investigated. Four Fabry-Pérot cavity antennas, covered by different Frequency Selective Surfaces, are discussed which are fabricated on a Quartz disk to guarantee mechanical stability and also for ease of fabrication, probing and measurement. A planar feed, a slot dipole fed by a coplanar waveguide, is also designed to excite the cavities. Prototypes have been designed and fabricated at central frequencies in frequency range of 42 to 46 GHz with various gains; however the same design can be adopted at higher frequencies. Full-wave simulations, done by Ansys HFSS, are verified with measurement results. © 2011 IEEE.