Facilitating collaborative knowledge work is a crucial issue in management: knowledge is a key corporate asset, but it is typically spread across various people in different organizational functions. In this paper we explore how conceptual visualizations (such as diagrams, visual metaphors, charts, sketches) can be constructed and used as cognitive artefacts that support collaborative knowledge work. In order to facilitate tasks such as the creation and sharing of knowledge in teams, we propose a collaborative dimensions framework as a tool for understanding how visual artefacts can facilitate collaboration in circumstances that involve distributed knowledge. The framework is based on the widespread Cognitive Dimensions of Notation framework and is enriched with criteria from the boundary object paradigm discussed in organization science. The dimensions of the framework are described and then applied to three different visualizations that are used in collaborative knowledge work. A discussion of future research needs concludes the paper.