One of the main problems in the design of high intensity rf accelerators is the presence of higher order modes (HOMs) which might degrade the beam quality. Accelerating cavities require HOMs suppression, whereas keeping a high quality factor (Q) for the fundamental mode. Both these requirements can be hardly met in closed metallic cavities, especially at high frequency where the configurations become cumbersome and technically unviable. Cavities based on photonic band gap (PBG) concepts showed that HOMs can be efficiently suppressed without affecting the fundamental mode. We present here simulations and measurements at room and cryogenic (77 K) temperature on some metallic (Copper) and metallo‐dielectric (Copper + sapphire) PBG based cavities, in order to study their rf behavior as resonant element in particle accelerators. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2486–2491, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22016