Green photoluminescence (PL) is observed from an as-anodized porous Si wafer immersed in the anodization electrolyte and the PL turns red after the sample is removed from the electrolyte and is blown dry. The PL of porous Si immersed in alcohol exhibits a blue shift and a marked decrease in intensity relatively to dry, as-anodized wafers. However, when the immersed samples are treated with UV for a few minutes, the PL peak shifts to a longer wavelength. Fourier-transform infrared spectroscopy reveals that alkoxy surface species and silicon hydride species backbonded to oxygen atoms appear on the UV-treated samples. Furthermore, the PL characteristics and surface species of the UV-treated samples can be recovered to those of as-anodized wafers by dipping in HF. These results point out the importance of surface chemistry in the luminescence process of porous Si.