This paper presents the results obtained in constructing and implementing a general framework for performing a comprehensive comparative assessment of electricity supply chains and strategies within the inter–agency join project on DECADES (Databases and mEthodologies for Comparative Assessment of Different Energy Sources for electricity generation). The project was established in 1992 by nine international organisations. A short description of the DECADES project objectives, structure and main components is given. The technology inventory databases, which are a major part of the project, address all the levels of different energy chains, from fuel extraction through electricity generation to waste disposal. These databases support comparative assessment in the power section, by providing generic information as well as country or region specific information on existing technologies and on those expected to enter the market in the next two to three decades. The paper further touches on the types of assessment that can be carried out using the methodology and databases developed. It points out in this regard the possibilities and limitations of comparative assessments performed at the level of power plant, full electricity supply chain and country or region electricity generation system. Illustrative results are presented for comparisons performed at all these levels. Case studies, workshops and seminars are some of the main activities carried out until now for validation and dissemination of the DECADES Computer Tools. In those studies, where it was considered, nuclear power appears to be cost effective for reducing emissions of CO2, SO2, NOx and other greenhouse gases. Finally, the paper briefly introduces the activities envisaged for phase II of the DECADES project, which will focus on disseminating current computer tools, providing training in the use of the tools and supporting country studies and on the development of new analytical capabilities. The paper concludes with some findings and remarks pointing out the usefulness of the integrated framework for comparative assessment developed within the DECADES project in support of decision making.