Abstract We present our investigations on the absorption and emission properties of the neutral oxygen vacancy in ZnO. Temperature-dependent photoluminescence (PL) experiments allow to determine the zero-phonon-energy of the emission and its phonon-coupling parameters. The absorption to the singlet excited state is observed in PL-excitation experiments at energies above 3.1 eV. Relaxation drives the system from the singlet, diamagnetic, excited state to the emissive, paramagnetic triplet state. Applying the Mollwo–Ivey relation for the energetical position of the F-centre absorption as a function of the anion–cation distance, we find that the oxygen vacancies in ZnO fit perfectly in the line given by MgO, CaO, SrO and BaO.