In this dissertation, we present a coherent analysis of the System Dynamics approach and a thorough review of some of the main SD software tools. The quintessence of the dissertation was the implementation of the System Dynamics approach in the development of a tool, where we tried to model the online deliberation process for a policy topic, that may potentially coexist with the official legislative procedure of the European Union. This process often coincides with the official policy making procedure, and, hence, can highly affect or be affected by it. Therefore the analysis and development of the model has been done under the framework of the EU legislative procedure. The model incorporates a set of metrics that depict the participation and engagement of the involved social actors at a given time that can be predicted through the execution of simulation scenarios. The proposed approach has been partially validated through real historical data obtained around various popular policy topics. The results obtained through the application of three alternative scenarios, showcased the main patterns, throughout an online discussion, and as well how and to what extent individual reactions, stakeholders’ behavior and external factors can affect the participation and involvement of a policy debate and what can influence its direction.