Results of a laboratory experiment on Decision Support System (DSS) use indicated that (a) active involvement in model building and data entry, (b) familiarity with model execution and the decision situation, and (c) consistency between a normative solution and the alternative encouraged by the problem frame led to an illusion of control, defined as an unwarranted inflation in expectations of success. Furthermore, higher expectations of success were associated with greater user satisfaction, better mood, and lower preference for thinking more before making the final decision. Higher expectations of success were less likely to be associated with preference for creating another model but were more likely to be associated with preference for further refinements to the existing DSS model before making the final decision. However, variations in expectations of success induced by sources of illusion of control were not associated with variations in decision performance. Implications for practice and research are presented.