This paper attempts to provide some answers to the following questions: when a shared position is reached as a result of a deliberative practice, what features determine such consensus? Is preferences change stable? Our analysis will focus on learning and dialogic quality of discussion as features that make the outcome stable, despite the characteristics of individual actors. We examine a successful case of public deliberation, i.e. a Citizens' Jury that reached a common solution about measures reducing air pollution through traffic regulation. To develop our analytical framework we look first at aggregate preferences change, as revealed by answers to a questionnaire administered to jurors before and after the Jury; second, we look at preferences change at individual level, as detected through the analysis of interaction, language and attitudes of each juror in the phase of deliberation.