We describe here the experimental conditions under which the photoelectrochemical etching (PEC-etching) of n-type silicon in HF induces the formation of porous silicon. Two types of porous silicon are formed underneath an etch crater : a layer of nanoporous material with pores in the nanometer range on top of a macroporous layer with pores in the micron range. The form of the macropores changes with the crystallographic orientation. We report on the evolution of these different features with the quantity of charge passed during the PEC and other etching parameters.