In this paper, a new approach is presented to assess the risk of using commercial off-the-shelf (COTS) devices in space systems under consideration of radiation effects that can dramatically affect reliability and performance. In the NewSpace era, the use of COTS has become mandatory, since typical space-qualified (class-1) electrical, electronic and electromechanical (EEE) components for space missions are no longer attractive due to their extremely high costs, long lead times and low performance. This paper sets out the usual constraints for COTS devices and proposes a guideline on how to select non-space-qualified components and when class-1 EEE devices are recommended for use.