Evaluating DSS involves examining multi-dimensional attributes associated with the value of DSS though the analysis of costs and benefits, changes in the decision process, and the quality of decision support systems. In the early 1990s, DeLone and McLean presented the IS success model as a framework and model for conceptualizing and operationalizing IS (including DSS) success. The DM model is one of the widely recognized IS models based on a systematic review of 180 studies which investigated over 100 success measures. An important assumption of the DM model is that it is the model to explain IS success in a voluntary IS use context. Due to the voluntariness of IS use, the “use” of the system is in the center of the model. This paper empirically tests the validity of the DM model in an e-learning environment and found out that the DM model failed to support the positive relationships between system use and system outcome. Can the DM model of IS success be applied to evaluate the DSS success? The answer may be probably no. The future research is needed to construct a comprehensive model for evaluating DSS success. The “use” may no longer be a critical construct in evaluating DSS success in that a substantial portion of DSS published seem to be mandatory or semi-mandatory.