Comparison-Shopping websites (e.g. MySimon.com) help consumers to select and compare products in the online shopping process. The influence of these information-aggregating intermediaries on consumer decision-making has been a focal interest in Information Systems area. In this research, we argue that it is alternatives set composition (i.e., the list of branded and non-branded products) rather than alternatives set size that affects consumer choice behavior. We conducted a series of experiments to investigate the impact of alternatives set size and alternatives set composition on consumers’ decisions. Our findings provide much support to our proposition that as the proportion of branded products increases, decision-makers are more likely to be not inclined to make a choice. However, in the event that buyers do make a purchase, they are more likely to choose a non-branded product. Implications for future research and practice will be discussed.