Standard cost benefit analysis as applied in economic practice and studied in the relevant literature means a quantitative assessment of feasibility and justification of an investment project. The decision on execution of an investment project is normally based on such an analysis, but it is left to the investor’s discretion either to prepare it or not. However, every activity in the space unavoidably impacts the environment and this is true for investment projects as well. Generally, an analysis should determine whether or not the project warrants a balanced approach to environmental protection in harmony with sustainable development, taking also into account the investor’s business goals. Sustainable development pursues and tolerates investments aiming at making profit, however part of such a profit must contribute to environmental protection. Such an approach is essential in order to ensure sustainable development; this is a closed circle which does not have any alternative. Accordingly, it is the responsibility of the investor, as determined by relevant legislation, to prove that the planned project will not adversely impact the environment. Faculty of Civil Engineering in Osijek has developed a methodology for preparation of cost benefit analysis in environmental impact assessment, as an outcome of a scientific project financed by the Ministry of Science, Education and Sport. The methodology has already been applied in a number of environmental impact assessments. This paper presents the methodology and its application as well as the role of communication in the process of preparation and approval of environmental impact studies.