Bundling is a very popular sales-promotion tool, in which a critical issue is to decide what products should be sold together in order to improve sales. Traditionally, this decision is based on the order data collected from the points of sale. However, Internet marketing now allows marketers to efficiently collect not only order data but also browsing and shopping-cart data, which provide marketers with information on the consumers’ decision-making processes, rather than only the final shopping decisions. The present study aimed to determine the value of this newly available information by comparing the performance of decision-making on product bundling based on three types of data on online shopping behaviors. The results from a field experiment reveal that significantly better decisions are made on the bundling of products when browsing and shopping-cart data are integrated than when only order data or browsing data are used.