AbstractIn this letter, the miniaturized bandstop filter with lumped capacitor element is presented. The resonator is based on a stopband characteristic of U‐shaped defected ground structure (DGS) section. Lumped capacitor element is embedded into DGS section without altering the geometry. The resonant frequency of DGS section is significantly lowered in accordance with increase of capacitor value. The DGS section with different capacitance values is designed and fabricated. From the measured results, size reduction over 60% is achieved by this method. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 802–804, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24152