AbstractCapacitively loaded coplanar waveguide (CPW) open‐loop resonators (OLRs) are proposed for maximum miniaturization in uniplanar microwave applications. It is shown that these resonators can be used to achieve a slow‐wave effect without occupying extra surface area. Also, the resonators have a size reduction of about 50% at the same resonance frequency, as compared with the conventional open‐loop resonator, as well as a higher performance of about 25–30%. The reduction in size of these types of resonators, and their performance (mainly the Q factor), can be controlled by the fingers within the OLR. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 298–300, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11042