The article discusses the development of the Estonian boundary, especially the mainland boundaries with Latvia and Russia. The Estonian-Latvian boundary was demarcated in the landscape in 1922-1927 and was not subject to change during the Soviet period 1940-1991. By the Tartu Peace Treaty of 2 February 1920, a new internationally recognised Estonian-Russian boundary was applied, which was changed to Estonian disadvantage after the Soviet annexation in 1944/45. Russia rejected a request to restore the boundary according to the Tartu Peace Treaty, submitted by Estonia after it regained its independence in 1991. The negotiations held in 1994 resulted in agreement to exchange only some small mainland and water areas.