The effect of changes in Li content on the structural property of sol-gel Li-doped ZnO films was investigated in this study. The observed changes of the Li incorporation-induced strain along c-axis are closely related to the different ratios between the concentrations of Li interstitials (Li-i) and Li substituting for Zn (Li-Zn) in the films. According to the observed results from X-ray diffraction (XRD) and photoluminescence measurements, we found that the domination of the dissociative mechanism in the Li-doped ZnO films led to transformation from Li-Zn to Li-i, involving the formation of Zn vacancies (V-Zn). In addition, the interaction between these defects (that is, Li-Zn, Li-i, V-Zn and oxygen vacancy) and the crystal structure may lead to the abnormal shift of the (0 0 2) diffraction peak position determined from XRD measurements. (C) 2010 Elsevier B.V. All rights reserved.