Inorganic nanostructures have been intensively studied because of their size-dependent emission color as a result of quantum confinement effects. In contrast, no significant size dependence of the optical properties is-expected for organic nanostructures. owing to the weak nearest-neighbor interactions in molecular crystals; however, the optical properties of organic materials can be significantly affected by aggregation and molecular packing, which can result in large differences between the emission spectra of solutions and thin films. Thus, the emission spectra of organic nanostructures may differ considerably from the bulk material despite the absence of quantum confinement effects. We demonstrate that 3,4,9,10-perylenetetracarboxylicdiimide (PTCDI) nanoclusters grown on ZnO nanorods exhibit an intense blue-white photoluminescence, different from the weak red emission of PTCDI films. Light emitting diodes consisting of ZnO nanorods and PTCDI nanoclusters also exhibited white emission.