The optical and electrical properties of porous silicon microcavities are strongly dependent on the environment. For highly luminescent samples both the luminescence intensity and the peak position are affected by organic substances, which also strongly modify the electrical conductivity, giving the possibility to obtain a multi‐parametric optical/electrical sensor. The peak position depends on the refractive index of the organic compound, whereas the luminescence intensity depends on its low frequency dielectric constant. Electrical properties depend on the dipole moment of the molecules. This allows discriminating between different organic substances.