Polybithiophene (PBT) can be deposited anodically within the pores of porous silicon (PS) from an organic electrolyte under mild conditions. Three different stages of the polymerization are observed : (i) silicon oxidation and PBT nucleation, (ii) growth of PBT (iii) formation of a PBT overlayer. The system PBT/PS was characterized electrochemically and by means of electron spectroscopy for chemical analysis and scanning electron microscopy. A complete oxidation of the PS is not observed. By X-ray photoelectron spectroscopy depth profiling and variations in the thickness of the porous silicon layers the growth of PBT within the pores was proved. Two different models for the polymerization process are discussed.