The present study sought to determine whether children discriminate between different group types with respect to perceived entitativity, and if so, whether the group properties that determine their perceptions of entitativity differ from those of adults. Ten-year-old children and adults were required to rate 12 social groups on a number of properties, including entitativity. In a further task, participants also sorted 30 social groups into discrete group types. Two major findings emerged. First, over the two tasks both children and adults were found to classify groups in terms of at least four main group types: Intimacy groups, task groups, social categories and loose associations. Second, children and adults appeared to have different perceptions concerning which group properties determine the degree of entitativity of the different group types. In particular children put much more emphasis on the level of interaction among group members whereas adults emphasized the importance of the group among its members. Copyright (C) 2010 John Wiley & Sons, Ltd.