This paper evaluates & compares, through electrical simulation, the immunity of multi-stage current starved voltage controlled oscillators (CSVCOs) and ring oscillators (ROs) submitted to direct power injection (DPI). All circuits were designed and simulated in the 180 nm 5 V XFAB-SOI process, with matching dimensions. The failure criteria selected were the output frequency, peak-to-peak voltage and DC offset voltage. Results demonstrated, that CSVCOs were sucsceptible at lower DPI frequencies, while the ROs were susceptible at higher frequencies. Both were impacted by different failure criterions. Regardless of the oscillator category, a higher number of inverter stages resulted in lower susceptibility to incident power levels. As a consequence of increasing the power level of RF injections, the highest DC supply current and output power, monitored for each oscillator was close to their nominal output frequencies. These circuits are currently being fabricated in a test chip and immunity measurements will be performed on it.