Optical properties of circular grating resonators in a silicon-on-insulator system are investigated numerically. These structures are of interest as building-blocks of integrated photonic devices. We use a time-harmonic 3D finite-element solver for studying transmission of waveguide modes through the system. We compare numerical results to experimental findings from the literature.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.