This work includes addenda to the paper entitled photoluminescence and electron paramagnetic resonance studies of defect centers in porous silicon (PS) which was published in this journal. The readers can readily obtain the principal values of g(parallel to) and g(perpendicular to) from the de-convolution of the effective principal g-values of the spin resonance data measured at various rotating angles of the magnetic field and the crystal axes. (C) 2002 Elsevier Science B.V. All rights reserved.