Due to technology scaling, devices are getting smaller, faster and operating at lower voltages. The reduced nodal capacitances and supply voltages coupled with more dense and larger chips are increasing soft errors and making them an important design constraint. As designers aggressively address the excessive power consumption problem that is considered as a major design limiter they need to be aware of the impact of the power optimizations on the soft error rates(SER). In this chapter, we analyze the effect of increasing threshold voltage and reducing the operating voltages, widely used for reducing power consumption, on the soft error rate. While reducing the operating voltage increases the susceptibility to soft errors, increasing the threshold voltages offers mixed results. We find that increasing threshold voltage (Vt) improves SER of transmission gate based flip-flops, but can adversely affect the robustness of combinational logic due to the effect of higher threshold voltages on the attenuation of transient pulses. We also show that, in certain circuits, clever use of high Vt can improve the robustness to soft errors.