This paper presents the results of SPICE simulations of terrestrial radiation induced effects on SRAM cells in which resistive-open defects are introduced. This kind of defect is difficult to be detected with standard manufacturing tests. Although the presence of the defect may not affect the memory functionality when not exposed to radiation, it alters the radiation induced error rate of the cell both under static and dynamic conditions. Moreover, the defect can increase the SRAM radiation-induced error rate when operations are applied to the cell (dynamic mode). For the purpose of estimating the impact of resistive-open defects on SRAM radiation sensitivity, we consider defects with different resistive values and compare the analytically calculated error rates during different SRAM operating modes.