Five commercial polycrystalline ZnO samples with different morphologies (nodular and needle-like) have been studied. Nodular ZnO crystallites reveal lower polydispersity, higher ultraviolet luminescence (380 nm), low green luminescence (500 nm), a small ESR signal with g=1.96 and a density close to the theoretical value for ZnO with the wurtzite structure. Needle-like ZnO crystallites have a higher polydispersity, higher green luminescence, higher ESR signal with g=1.96 and lower values of density. The observed differences in the physical properties are associated with the presence of oxygen vacancies in needle-like particles and probably also interstitial zinc atoms in nodular particles.