A new coplanar waveguide bandstop filter using capacitively loaded spiral-shaped resonator is proposed. The filter consists of a rectangular stepped coplanar waveguide and a spiral-shaped slot in the center conductor. BY embedding capacitor in the spiral-shaped slot, notable bandstop filter can be implemented, and tuning range from 1.5 to 3.0 GHz have been obtained. (C) 2009 Wiley Periodicals. Inc. Microwave Opt Technol Lett 51: 3001-3004, 20ft Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24769