This study investigated tutoring during collaborative role-play dealing with environmental dilemmas in a synchronous network environment. The relationships of different tutor scaffolding styles with students' discourse acts and their decision-making variables were studied. A role-play with a jigsaw design was developed using the model of real-life environmental negotiations. Tutor scaffolding supported the process of making judgements. Five role-plays consisting of 31 decision-making discussions were carried out with 14-17-year-old students (N=62) from Estonian secondary schools. The findings indicated that the activeness of tutor scaffolding was related to the higher frequency of students' task-related discourse acts, as well as their ability to generate a mutually accepted ownership of problem representations in teams.