Radiation defects in electronic device can occur in a process of its fabrication or during use. Miniaturization trends in industry and increase in level of integration of electronic components have negative affect on component’s behavior in a radiation environment. The aim of this paper is to analyze radiation effects in semiconductor memories and to establish how ionizing radiation influences characteristics and functionality of semiconductor memories. Both the experimental procedure and simulation have been used to investigate the behavior of irradiated semiconductor memories. EPROM and EEPROM commercial semiconductor memory samples have been exposed to indirect ionizing radiation to test their radiation hardness. Monte Carlo simulation method has been used to analyze the effect of direct ionizing radiation on semiconductor memory.