Effect of phase condition (crystallinity) on the low-temperature radiation-induced degradation of polycarbonate was studied by electron spin resonance (ESR) and infrared (IR) spectroscopy. Semi-crystalline polycarbonate exhibits lower relative yields of radiation-induced degradation in comparison with amorphous polycarbonate, as evidenced by monitoring of both CO and CO2 formation (IR spectroscopy), and radical pair formation (ESR spectroscopy). On the basis of results obtained, the mechanism of electron stabilisation in polycarbonate, and reasons of variation in radical pair inter-spin distance are discussed.