In this paper, the resonant frequency and quality factor of a novel coplanar waveguide (cpw) diamond shaped resonator was analysed using Advanced Design System (ADS-2009) finite element software. The diamond resonator was compared with the cpw radial stub resonator on gallium arsenide (GaAs); the work indicated that the diamond resonator had a smaller physical size and higher quality factor (Q) at milli-metric wave frequencies. Experimentally measured diamond cpw resonators fabricated on gallium arsenide (GaAs) were in good agreement with the simulated results.Index Terms-Diamond resonator, resonant frequency, radial stub resonator and quality factor