Raman scattering and photoluminescence measurements have been performed in free standing porous silicon, for the first time at hydrostatic pressures up to 21 GPa. The pressure dependence of the porous silicon photoluminescence and Raman scattering has been systematically investigated as a function of porosity. Spectral features of both the Raman and PL bands exhibit almost the same transition pressures and depend on the maximum pressure achieved. Highly porous silicon (>80%) transforms at 18 GPa resulting in unrecoverable suppression of Raman and luminescence activity.