The properties of metal (Al, Au)-anodic oxide-CdSnAs2 monocrystal structures are studied. It is established that MOS-structures using undoped CdSnAs2 crystals show a high positive fixed charge in the anodic oxide (NS≃ 5·1012 cm-2) and high surface state density on the oxide-CdSnAs2 boundary surface (NSS ≃ 2·1013 cm-2·eV-1). In MOS-structures using diffusion-doped (copper) crystals the sign of the fixed charge is negative (NS ≃ 1011 cm-2, NSS ≃ 2·1012 cm-2·eV-1). The latter structures show a definite photosensitivity and photomemory. The possibility of effective control of the fixed charge value within the oxide by illumination is shown. The surface state distribution over energy, time constant, and capture section is determined.