The aim of this paper is to present some methodological aspects connected with the evaluation of the growing market of goods facilitating protection of the natural environment. This is a positive phenomenon in this age of ever increasing attention paid to the implementation of principles of sustainable development as well as decreased barriers for improving access to developing markets in the case of both economically highly developed countries and in developing countries. The elimination of trade barriers in foreign trade for goods and services also increases the efficiency of the global economic system by enabling countries to specialize in those sectors in which they possess economic advantages, including those sectors in which they possess favorable natural environmental conditions. The analysis of these goods and services is related also to some regulations of the Committee for Trade and Environment of the WTO, with special reference to conclusions of the Fourth and Fifth Ministerial Conferences in Doha and Cancun. As a member of the European Union, Poland should side with an acceleration in negotiations relating to the quick opening of environmental services markets within the framework of the Doha Round. In the sphere of what is known as development assistance, companies from the “old” and “new” members of the EU may undertake investments in developing countries and provide consulting in this realm, as well as deliver capital goods for improving the state of the natural environment, mainly aimed at working against excessive greenhouse gas emissions into the atmosphere and against unfavorable climate changes.