In this paper, we focus on the preferential treatment of buyers by their suppliers. As there is a lack of detailed information regarding the reasons that suppliers serve some buyers better than others, our research addresses a supplier's evaluation of customers and how this evaluation can be influenced by buyers. To give an overview of the drivers of preferential treatment by suppliers, the provided literature review covers three research fields that are considered crucial to this issue: (i) customer attractiveness, (ii) supplier satisfaction and (iii) preferred customer status. By integrating these research topics, we provide a state-of-the-art analysis and overview of the various drivers of preferential treatment, build a preliminary conceptual model and suggest several directions for future research. The identification of the drivers and the resulting conceptual framework can serve as a stepping stone for additional research in this new field.