Background Multi-criteria decision analysis (MCDA) has emerged as a formal methodology for fusing available technical information and stakeholder values to support decision-making in many fields. MCDA has many characteristics, such as the integration of diverse information and the handling of conflicting objectives, which make it a useful tool for supporting environmental impact assessment (EIA) and Strategic Environmental Assessment (SEA) processes. Both EIA and SEA are policy procedures developed as a response to environmental problems that arise from development. EIA is applied to projects, while SEA applies to policies, plans and programmes. Practices for evaluating the impact of alternative approaches to environmental planning are underdeveloped, and public participation produces information that is not used efficiently. As a result, it is necessary to demonstrate that the integration of the MCDA into EIA/SEA and efficient interaction between stakeholders have a crucial impact on the quality and effectiveness of EIA and SEA procedures. This LIFE project will thus cover an important area in environmental planning that has not been addressed to date. Objectives The overall aim of the 'IMPERIA' project is to bring good practices and methods from MCDA, developed and applied extensively by the project partners, to the fields of EIA and SEA. The project also aims to increase collaboration and information exchange between EIA/SEA, MCDA and participatory planning professionals (authorities, planners, consultants and researchers all over Europe). The project will demonstrate via three pilots the ways in which MCDA can be used in EIA and SEA processes to improve the comprehensive evaluation of alternatives and more explicit evaluation of impact significance. The specific objectives of the project are: To develop systematic, transparent and participatory practices and procedures by integrating principles and practices of MCDA into the EIA and SEA processes; To demonstrate the ways in which MCDA can be used in EIA and SEA processes to improve the comprehensive evaluation of alternatives and more explicit evaluation of impact significance; To develop new MCDA-based tools for integrated EIA and an MCDA-based questionnaire tool to gather public opinions online in a structured and efficient way; and To compile guidelines for the integrated and interactive use of MCDA principles and tools in EIA/SEA processes. Expected results The project will result in improved quality, transparency and participation in EIA and SEA. The findings of the project will be useful for the development of European strategies and policies for EIA and SEA, in particular, how to increase the effectiveness of citizen and stakeholder participation and the cost-effectiveness of the EIA procedure. The project outcomes also are expected to be highly applicable to environmental planning and natural resources management and policy-level decision making. For instance, they will be highly relevant to the “EU liaise” project, which aims at developing and providing tools to improve dialogue between scientists and policy-makers. Other results will include: An MCDA-based tool and procedure to support stakeholder involvement in different phases of EIA and SEA. To this end, a group of approximately 10-20 representatives from various interest groups will be established; Creation of a generic questionnaire format for gathering stakeholder and public views and opinions tailored to support the evaluation of alternatives and impact significance determination; A web tool for gathering public views and opinions relevant to the EIA process; The creation of the “YVAKO Web service”: a web-platform for EIA in both Finnish and English; and A two-to-three-day training course for different actors in the EIA and SEA fields related to the practices and tools developed by the project.