Group decisions are ubiquitous in everyday life. Even when decisions are made individually, decision-makers often receive advice or suggestions from others. Thus, decisions are often social in nature and involve multiple group members. The literature on group decision-making is conceptualized as falling along two dimensions: how much interaction or information exchange is allowed among the group members, and how the final decision is made. On one end, group decisions can be made simply by aggregating member preferences or judgments without any interaction among members, with members having no control or say in the final judgment. One the other end, groups’ decisions can involve extensive member interaction and information exchanges, and the final decision is reached by group consensus. In between these two endpoints, various other strategies are also possible, including prediction markets, Delphi groups, and judge–advisor systems. Research has shown that each dimension has different implications for decision quality and process depending on the decision task and context. Research exploring these two dimension has also helped to illuminate those aspects of group decision-making that can lead to better-quality decisions.