This paper reports an empirical study comparing the role of discourse and knowledge representations (graphical evidence mapping) in face-to-face versus synchronous online collaborative learning. Prior work in face-to-face collaborative learning situations has shown that the features of representational notations can influence the focus of learners' discourse and collaborative activities. Two hypotheses were considered in the present study: (1) The influence of knowledge representations in the online condition could be weaker because of the lack of shared awareness and meaning that results from working together in front of a physically shared display, and because of the greater difficulty of utilizing the representations as a resource for conversation through gestural deixis, and (2) The influence of knowledge representations in the online study could be stronger because participants must rely more on them to compensate for the absence of face-to-face modes of communication. Quantitative results largely support the second hypothesis. There was greater consideration of certain coding categories supported by the knowledge representation software. However, essay quality and other observations provide indirect support for the first hypothesis. Explanations for these results and implications for the design of online collaborative learning environments are provided.