The optical properties of thin films of two different quaterthiophenes, unsubstituted and substituted, deposited on different substrates by organic molecular beam deposition are briefly illustrated. The absorption spectra of the samples present both the molecular exciton peak, characteristic of strongly interacting molecules and polarized along a preferential direction in the most ordered films, and small bands coming from less interacting or misaligned molecules; these are mostly responsible for the photoluminescence spectra.