Neutron-irradiated Czochralski grown Si subjected to heat treatment (HT) at 350C and 1000C under enhanced hydrostatic pressure (HP) was studied. It was shown that external hydrostatic pressure enhanced the creation of VO2 defects in neutron-irradiated Si subjected to the HP - HT treatment at 350C. Enhanced formation of platelet-like O precipitates was found in the samples treated at 1000C under 1.1GPa. This effect was more pronounced in the samples with VO2 defects. Presented results seem to suggest that probably HP helps to transform VO2 to some kind of defects or change lone VO2 defects into a form that could act as an additional nucleus for an additional O precipitation at 1000C. No correlation between the plate-like O precipitates related absorption at 1225/cm and dislocation-related emission was confirmed.Optical Studies of Defects Generated in Neutron-Irradiated Cz-Si during HP-HT Treatment. B.Surma, A.Misiuk, A.Wnuk, C.A.Londos, A.Bukowski: Crystal Research and Technology, 2005, 40[4-5], 471-6