The change in surface chemical contents and photoluminescence spectra of porous silicon are investigated after etching in argon plasma with oxygen admixture. Such a treatment leads to the saturation of dangling bonds by fluorine and to formation of silicon oxide on surfaces of quantum wires. After a preparation of porous layer, HF acid remnants inside voids become a source of fluorine, whose concentration grows accompanied by an increase in the greenish-blue photoluminescence band as well as red band broadening. It is shown that the surface fluorination does not influence the laser-irradiation-induced degradation of porous silicon photoluminescence. (C) 2002 Elsevier Science B.V All rights reserved.