The performance and reliability of electronic devices in harsh environments depend on the response of these devices when they are inevitably subjected to different radiation effects in applications as complex as space-borne systems. Electronics devices, thus, may experience degradation which may damage and/or result in device failure. This paper presents the effects of ionizing radiation on the C-V characteristic, as a diagnostic tool, of the SOI-MOS capacitor (SOI-MOS-C) at room temperature. These effects are examined before and after exposing the capacitor to radiation at high frequency (HF). The radiation effects influence on the C-V curves is reviewed under different radiational dose conditions. The irradiated capacitors exhibit changes in the capacitance. Increasing irradiation dose results in increased capacitance values and a shift in voltage values. The change in the C-V curves is ascribed to variations of charge accumulation and the generated electron-hole pairs as well as the increase of interfacial states at the buried oxide (BOX)-Si interface. Appropriate protection of these devices in these harsh environments is also essential to ensure proper operation of the devices and to exclude undesirable effects. It is concluded that C-V characteristic of SOI-MOS-C is a suitable tool for characterizing electronic devices in harsh environments, such as space applications, and SOI technology offers an alternative choice for radiation-hardened devices. The usefulness of HF SOI-MOS-C C-V characteristics is also discussed for device modeling in such cases. The effect of voltage sweep direction during C-V measurement is also discussed.