The structural and light-emitting properties of porous Si prepared from differently doped p-type Si (111) substrates have been studied by Raman scattering and phoioluminescence (PL). A detailed analysis of the Raman line shapes was performed using a quantum phonon confinement model with realistic LO and TO phonon dispersion curves. Prevailing Si nanocrystallite types (spheres or wires) and characteristic sizes were determined for samples with porosities from 30 to 80%, The highly porous samples consist of fine Si spheres, while those of lower porosity are mostly wire-like. The PL spectra are less size-sensitive than the Raman ones and no clear correlation between the structural information from the Raman scattering and the PL has been observed.