Emerging applications of porous silicon (PS) lies in its ability to incorporate other materials, such as organic groups, organic and inorganic nanoparticles to form (bio)hybrid systems where each individual constituent may be optimized for a particular function. This paper presents our recent experimental results on the fabrication and applications in biosensing of the porous silicon (PS) based microstructures. We have demonstrated that different morphologies of PS, either as-prepared or coated with gold nanoparticles have an important role in biomolecule detection, due to its large internal surface combined with specific electro-optical properties, being in the same time support for immobilization of complementary biomolecules as well as transducer for biochemical interactions. Therefore, we have investigated the photoluminescence properties of nanoporous Si prepared on different Si micropatterned surfaces comparatively with PS/flat Si in order to develop a new simple and versatile process for biosensor transducer fabrication. Meso- and macro-PS have been investigated for protein immobilization and detection using microarray technique or for DNA biomolecule detection by impedance spectroscopy. Finally, we have demonstrated that macroporous silicon constitutes an appropriate substrate for very sensitive SERS biosensors. RAMAN signal of 11-mercaptoundecanoic acid was investigated on Au/macroporous silicon. Various characterisation techniques have been used, optical and scanning electron microscopy (SEM) to investigate samples morphology, X-ray diffraction for nanoparticle structure, Raman and PL spectroscopy, and laser fluorescence detection for chemical and optical properties analysis and impedance spectroscopy for investigation organic molecule attachment on the Au/PS structures.