Discussions on participation of the Republic of Moldova within different integration processes are intense. In order to ensure a better understanding of these processes, doctrinal analysis of terms like ”free trade zone” and ”customs union” is indispensable. Under these conditions we defined ”free trade zones” as a way of extending the customs territory, including two or more customs territories, aiming at total elimination of customs duties and restrictive trade regulations between the member countries, while the ”customs union” represents the replacement of two or more customs territories by one, elimination of customs duties and restrictive trade regulations within this territory, and establishment of a common customs and trade regulation for third countries.