The objective of this study is to investigate the effects of different meeting modes and task types on the outcomes of group decision making. The hypotheses postulate the potential effects of different meeting modes on appropriation process; different meeting modes on group outcomes; and the appropriation process on group outcomes. A laboratory experiment was conducted. A GSS was developed using Lotus Notes for this experiment. The results provide partial support for the hypotheses derived from the theoretical model. The interaction effects between meeting modes and tasks are not always observed in the analyses. However, groups using a face-to-face meeting mode in negotiation task reach significantly higher levels of perceived outcome quality, of satisfaction with the outcome, and of satisfaction with the process than groups using a dispersed-synchronous meeting mode. It suggests that a face-to-face meeting mode can enhance the effectiveness of groups working on a negotiation task such as stakeholder analysis. Furthermore, the manner in which groups appropriate the technology significantly influence the group performance. The results support the validity and usefulness of the IRT and the AST as a GSS research framework.