Measurements of the angular correlation of annihilation radiation and infrared absorption spectra were conducted with porous silicon samples, containing capillary macropores with a diameter of about 1 m. The set of data shows that a high proportion of Si-O bonds contribute to positron annihilation and IR absorption for porous silicon. Annihilation parameters and estimated values of the specific surface area point to the availability of a nanoporous system in the macroporous silicon. Most likely the macropore surface is covered by the nanoporous material to a thickness of 100-200 nm. The characteristic size of the nanopores is estimated at 1-2 nm. Si-O bonds are located at the nanopore surface and do not exceed one monolayer.