The present thesis consists of three studies on the effects of group membership in large group decisions. The overall aim was to contribute to understanding how individuals react when decisions are made in large groups. We explored consequences of procedural justice concerns within such groups. In Study I we investigated how different decision procedures and issue importance affect perceptions of others who agree and disagree with the individual on a potentially important issue.  Individuals attributed more positive reasons for attitudes of those who agree as opposed to disagree with themselves, whereas disagreers were attributed more negative reasons. The asymmetry was moderated by decision form, and issue importance. The attitudes concerned attitudes towards potential new policies. In Study II we investigated differences in participants’ perceptions of others depending on own position towards the new policy. Challengers of the status quo advocating a change in the existing policy, were more biased when judging others than were defenders of the status quo. This suggests that challengers are less tolerant of defenders’ point of view. This effect was not affected by perceptions of minority status among the challengers. In Study III we looked at individual group members’ cognitive restructuring of a preferred decision alternative, and how it differs between decision conditions when the decision-maker is affiliated to own ingroup or not. Results showed that individuals restructure the attractiveness of their preferred alternative in group decisions similarly to what has been previously found in individual decision-making. The magnitude of restructuring was greatest when ingroup members decided for the group. However, this effect was moderated by identification with the ingroup, such that those who identified themselves with the ingroup restructured their preferred alternative more when ingroup members decided as opposed to when outgroup authorities decided. / <p>At the time of doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Submitted.</p>