ZnO nanostructures have been electrochemically synthesized on three-dimensional, interconnected, and porous carbon nanofiber Buckypaper substrates. Using potentiostatic deposition, wurtzite ZnO with controlled microstructure and morphology has been deposited. While all ZnO deposits exhibit a band gap value of around 3.2 eV, impurity states determined by photoluminescence (PL) measurements show strong deposition potential influences. Both the green and red emissions corresponding to respective oxygen vacancies and oxygen rich impurity states can be identified. Thermal annealing can greatly reduce oxygen vacancy concentration but has limited effects on the oxygen rich defects. This study suggests a cost-effective and high-throughput approach in deposition of ZnO nanostructures suitable for photovoltaic applications.