Cities around the world attempt to imitate the Silicon Valley model by adopting public policies aimed at attracting new high-tech industries and Research and Development activities. The adoption of Information and Communications Technologies (ICT) as elements in a public policy is based on the expectations of policy-makers regarding the potential to harness technology to ameliorate key urban problems such as a deteriorating environment, congestion or lack of communications between citizens and institutions. More specifically, policy-makers are exposed to knowledge about ICT, which is supplied by a variety of sources like scientists, popular media and their own experience. This paper argues that two gaps typify the flow of knowledge consumed by urban decision-makers: the knowledge gap, namely the uncertainty about the actual impacts of ICT on urban issues, and the communication gap which relates to the biases and noise emanating from the process of communicating knowledge between different actors on potential ICT impacts. The communications gap can, to a large extent, be explained by language and cultural differences between scientists and policy-makers. To illustrate and emphasise the gaps and their role in the ICT policy-making process, in this paper a comparison is made with the more familiar case of transportation policy making. © 2002 Elsevier Science Ltd. All rights reserved.