This dissertation studies important issues in supply chain management and marketing interface research: competition, product line design, and channel efficiency, at the presence of vertically differentiated products. Vertical differentiation as a means of price discrimination has been well-studied in both economics and marketing literature. However, less attention has been paid on how vertical differentiation has been operationalized. In this dissertation, we focus our study on two types of vertical differentiation: the one created by a product line which is produced by the same firm, and the one created by products from different firms. We especially are interested in the so-called private label products vs. the national brand products. Specifically, this dissertation explores how vertical differentiation can affect the interactions among the members of a supply chain in several different contexts. In the first piece of work, we use a game theoretic model to explore how the ability of a retailer to introduce a private label product affects its interaction with a manufacturer of a national brand. In the second essay, we are investigating how an original equipment manufacturer (OEM) will be affected by the entry of a competitor when there are strategic suppliers of a critical component. If these suppliers behave strategically, it is not clear that the entry of other players will necessarily be harmful to the incumbent. In the last work, we pay our attention to an emerging change happening in the industry: some retailers begin to sell their private labels through their competitors. We investigate the strategic role of a retailer selling her own private label products through another retailer. In summary, this dissertation illustrates how vertical differentiation play a crucial role in firms' supply chain as well as marketing strategies. Therefore, it is important for firms to recognize these strategic issues related to vertically differentiated products while making operations/marketing decisions. / text