In this paper, we report the experimental results on the optical properties of oligo-phenylene vinylenes (OPVs) formed in nanosize pores of porous silicon substrates. Strong modifications of the photoluminescence properties of nanosize aggregation of OPVs were observed at room temperature, such as a blue shift of the PL spectra, whereas the structure of the oligomers is preserved as proved by Raman scattering experiments. However, the penetration of the oligomers into the nanopores was found to depend on the conformation of the chains, which is, in turn, conditioned by the solvents, used to dissolve the oligomer powder.