The incorporation of hydrogen into Si, under different electrochemical conditions including anodization in fluoride solutions where porous silicon is formed, is studied by NRA and in situ capacitance measurements. Results suggest a large near surface concentration of H whilst simulation show that the maximum penetration depth is governed by volume diffusion of H and material removal. Diffusion coefficients are found to be dependent on electrochemical conditions and ranged between 10−13 and 10−11 cm2 s−1. The interplay of H permeation with porous silicon layer formation is discussed.