Organic/inorganic nanocomposites composed of a ploy(3-hexylthiophene) (P3HT) film and TiO2 nanotubes or ZnO-coated TiO2 (ZnO/TiO2) nanotubes were fabricated and the influence of the inorganic nanostructures on the optical properties correlated with their photoactivity was studied. The structures of the organic/inorganic nanocomposites were characterized by X-ray diffraction and Raman backscattering spectroscopy. The optical properties were evaluated by measuring the optical absorption and photoluminescence. The TiO2 nanotubes exhibit anatase structure and the ZnO coating is structured with hexagonal wurtzite. The inorganic nanostructures are fully covered by the P3HT films with some P3HT infiltrating into the lacunas of the one-dimensional nanostructures. The P3HT-covered TiO2 NTs show strong optical absorption and present evident photoluminescence quenching. Nano-heterostructured ZnO/TiO2 NTs are superior to nanostructured TiO2 NTs in composing organic/inorganic nanocomposites with P3HT. The presence of a thin ZnO coating between the P3HT film and the TiO2 nanotubes further increases light absorption and quenches photoluminescence, revealing efficient generation of excitons by optical excitation and suppression of radiative recombination of photo-generated excitons, and suggesting that the organic/inorganic nanocomposite P3HT-covered ZnO/TiO2 nanotubes exhibits high photoactivity and an enhanced light harvesting efficiency can be anticipated. The temperature-dependent photoluminescence was also measured for an examination of Pi-stacking aggregation and a discussion of exciton coupling in P3HT at different temperatures.