Abstract: A porous silicon thin layer was prepared by anodic oxidation under different corrosion conditionEmails. The layer thickness was a few tens of nanometers, which is much smaller than the average range of positrons from a 22Na source. The mean pore volume and specific surface area in the samples were measured with 22Na positron life spectroscopy, by measuring the bulk lifetime spectrum of porous silicon and then deducting the lifetime spectrum of the substrate.