Abstract A steady-state photoluminescence (PL) from hydrothermally grown ZnO nanorods is investigated. First, the temperature-dependent PL spectra of the as grown ZnO nanorods in the near-band-edge (NBE) region and in the deep-level (DL) region are discussed. Second, the description of the effect of annealing in nitrogen and in vacuum on the PL spectra at 4 K is given. Annealing in both nitrogen and vacuum significantly alter the intensity ratio of the NBE-to-DL emission and lead to greatly enhanced optical quality of the ZnO nanorods. Finally, the influence of the size of the ZnO nanorods on their 4K PL spectra is analyzed.