There is a huge variety of tools for synchronous collaboration including instant messaging, audio conferencing, videoconferencing and other shared spaces. One type of tool, collaborative virtual environments (CVEs), allows users to share a 3D space as if they are there together. Today, most experiences of virtual environments (VEs), including games and social spaces, are constrained by the form of non-immersive interfaces that they use. In this chapter we review findings about how people interact in immersive technologies, that is large-screen displays such as CAVE-like displays, and how they provide a number of advantages over non-immersive systems. We argue that modern immersive systems can already support effective co-presence in constrained situations and that we should focus on understanding of what is needed for effective and engaging collaboration in a broader range of applications. We frame this discussion by looking at the topics of co-presence, representations of users and modalities of interacting with the VE. Different types of immersive technologies offer quite distinct advantages, and we discuss the importance of these differences for the future of CVE development.