Recently mixed-anion compounds such as metal oxynitrides have attracted considerable attention in physics, chemistry and materials science. In the present brief review, we describe the structural analyses of the mixed-anion compounds. X-ray and neutron diffractometry is able to refine the crystallographic parameters of the crystalline mixed-anion compounds. Electron-density from X-ray data and neutron-scattering-length-densities from neutron data can give the information on the chemical bonding and structural disordering. Scanning transmission electron microscopy and electron energy-loss spectroscopy allow us to characterize local crystal structures with high spatial resolution. Combination of the information about local structures by X-ray absorption near edge structure and magic angle spinning-nuclear magnetic resonance with those available by the diffraction techniques is effective to tackle the problems peculiar to the mixed anion systems: discrimination of N^3－, O^2－, and F^－, and H^－ and OH^－.