Today, information and timely decisions are crucial for an organization’s success. A Decision Support System is a software tool that provides information allowing its users to take decisions timely and cost-effectively. This is highly conditioned by the quality of the data involved, usually stored in a data warehouse, and by a sound and complete requirements analysis. In this chapter we show that conventional techniques for requirements elicitation cannot be used in Decision Support Systems, and present a methodology denoted DSS-METRIQ, aimed at providing a single data quality-based procedure for complete and consistent elicitation of functional (queries) and non-functional (data quality) requirements. The outcomes of the process are a set of requirement documents and a specification of the operational data sources that can satisfy such requirements. We review the state-of-the-art in the field, and show that in spite of the tools and methodologies already proposed for the modeling and design of Decision Support Systems, DSS-METRIQ is the first one that supports the whole process by means of an integral technique.