This letter applies bent cavity resonators to realize a low-profile frequency selective structure exhibiting high selectivity of filtering response. The structure is realized through substrate integrated waveguide technology. Its unit cell includes three cavities that support TE101 and TE102 modes of rectangular waveguides. Couplings of these cavities with air is adjusted in such a way that two transmission zeros are produced near the skirts of a narrow passband. The concept of bent waveguides is proposed to reduce the overall thickness by 38%. A prototype is designed and fabricated with its frequency centered at 10.4 GHz. A relatively stable frequency response is exhibited for TE polarization, under a moderate variation (<30°) of incident angle. Measured results are in good agreement with those obtained through simulations.