In this work, we present a first-principles DFT study on the CLS of defects in a model metal oxide, involving both surface imperfections and bulk point defects. ZnO is used as a model metal oxide, because it is well-studied and widely used with versatile functionalities in electrical, optical, magnetic, dielectric and many other fields, where native point defects play a crucial part. Identification of these defects and correlating them with physical properties has been a key point of much research. Therefore, theoretical prediction of chemical shifts for defects in ZnO is of both high theoretical and practical interest.