Within the frame of the deliberative democratic theory, development of information and communication technology (ICT) has been proposed as a solution to enhance discussion in large groups and foster political participation among citizens. Critics have however underlined the limits of such technological innovations that do not generate the expected diversity of viewpoints. This paper highlights the limits of a Habermassian conception of deliberation, which restrains it to a specific type of rational discourse and harnesses citizens’ expression within strict procedural constraints. Our case study, the DUCSAI debate — that is, the French public debate about the location of the third international Parisian airport — shows that the added value of Internet-based deliberation rests in that it has widened both the participant’s profile, the nature of their argumentation and their means of expression. The use of ICT in this context has empowered the actors by giving them the opportunity to master the technical constraints of the debate.