Organizational decision support systems (ODSS) are a new type of decision support systems (DSS) focusing on the organization wide issues rather than individual, group, or departmental issues. Because of its organization wide scope, a typical ODSS cuts across organizational functions or hierarchical layers. Thus, seamless integration with organization's diverse IS applications running on heterogeneous platforms becomes a critical issue for building a successful ODSS. We analyze the Korea Telecom (KT)'s Operations and Maintenance (O&M) division focusing on its investment strategies. We develop a conceptual framework which links O&M investment decisions to performance of its operational branches across the nation. In this framework, performance of each local branch is evaluated on two dimensions: quality of service (QOS) and difficulty of the local operating environment (CDI: context difficulty index). This approach will enable O&M management to explicate the major causes behind differences in service quality among local branches and to determine proper scale and area of O&M investment for competing branches. To support the above framework, we also develop a prototype for the KTOM-ODSS with an EIS like user friendly interface. When a complete ODSS is implemented on top of various KT transaction processing systems, it will become a critical component of the O&M Integrated Decision Support Environment (IDSE).