Environmental impact assessment represents an effective preventive system against damage to the environment that is based on prognosis and assessment of presumed positive and negative impacts of development projects and policies. Primarily the acts on environmental impact assessment have had great influence on decision making processes in the sphere of environmental, social and economic development on national and global levels. The article analyses the contemporary research priorities on the basis of the results of important international conferencies and workshops, numerous of methodological guidelines, textbooks, final reports and studies in the area of environmental impact assessment. The main priorities in basic research are: cumulative effects analysis, decision analysis and relationships between the strategic environmental assessment and concept of sustainability; in applied research they are: evaluation of the results of the monitoring and post-project analysis, involvement of public in the assessment process and improvement of the effectiveness of the decision-making processes.