The dissertation presents marketing issues in which consumers are engaged in more than two activities related to marketing; cross-activity analysis. In particular, the dissertation suggests two marketing models to capture 1) consumers' choices of simultaneous and sequential bundle choices of related categories and 2) consumers' visitation on multiple social network services. Chapter 2 aims to propose a general framework to describe consumers' sequential bundling of items in related product categories and to compare their choices with those under simultaneous bundling situations. To achieve this, a dynamic model in which strategic consumers can choose a bundle either sequentially or simultaneously is developed. Chapter 3 presents a bivariate visitation model where users belong to multiple social networking services. In this model, I find various interdependency sources that affect users' visitations across multiple social networks; experience spillover, correlated sensitivities and unobserved components. Among various sources, I also discover a unique dependency source that come from social network structures across different social network services, that is, overlapping friends. Chapter 4 discusses potential extensions of the approaches that are presented in the dissertation.