Visual knowledge mapping diagrams or concept maps are pictorial tools used to organise and present knowledge. They include descriptions of concepts with linking lines as a representation of the relationships between the concepts. Concept maps have been used as part of a current study examining teachers' pedagogical reasoning around the inclusion of information and communication technology (ICT). As one method to capture teachers' reasoning, teachers have been asked to construct a concept map to explain their thinking and decision making when including ICT in the teaching. For this research concept maps have been used as a data gathering tool to provide clarity in identifying the key concepts of teachers' reasoning in planning to use ICT in their classroom. This paper will briefly provide an overview of the literature around concept mapping as a research tool, and examine the value as a data source for accessing the thinking behind teacher's decision making to use ICT .