At present time the process of environmental impact assessment of motorway building in Slovakia is culminating and the process of environmental impacts assessment of modernization of the railway-network is beginning. They are both connected with political endeavor to create infrastructural preconditions for economic development of Slovakia and its incorporation into European traffic network. Experience with environmental impact assessment of proposed parts of motorways points at certain problems the use of methods. At present time, motorway sections are being assessed in specific environment of Western Carpathians typical of mountain ridges (mainly protected as national parks or natural preservation areas), with narrowed valleys and isolated basins serving as the bases of settlement and economic activities. In this environment it is almost impossible to propose environmentally, technically and economically comparable alternatives, which is the precondition for multicriterial evaluation and the establishment of optimum alternative. The method of indicators includes only measurable impacts which causes political conflicts on public discussions, because the most important impacts for the inhabitants are the psychosomatic ones, the measurement of which is in limited time and concrete area impossible. This fact unavoidably requires stronger emphasis on the role of political subjects, in the process of the alternative choice for realization from the viewpoint of political priorities (environmental versus economic), because the environmentally convenient alternative is very expensive from the viewpoint of complicated natural and settlemental conditions in Slovakia. The priorities given by territorial plans completed in old economic-political conditions are at present often problematical.