Social networking system users may create events where a group of other users invited to the event meet at a specified time and location. While an inviting user initially specifies the group of users to invite to the event, the social networking system suggests additional users to invite to the event. The social networking system suggests additional users based on a prediction that the users would attend the event if invited. Various factors may be used to make the prediction, such as an affinity between the inviting user and the other users, the availability of the other users at the time of the event and/or the proximity of the other users to the location of the event. Invitations to the suggested additional users may be automatically sent or sent to a set of the additional users selected by the inviting user.