Zmijanje is an area in northwestern Bosnia, in the western part of the Republic of Srpska respectively, inhabited by Serbian population. In the administrative-territorial aspect Zmijanje does not exist as a separate organizational unit. It is located in the border area of the City of Banja Luka, as well as municipalities of Mrkonjić Grad, Sanski Most and Ključ. Published historical sources shows that Zmijanje existed throughout history as an administrative-territorial unit and that by the end of the 13th century Zmijanje is represented by Bosnian parish Zemljanik. During the Turkish conquest by the half of the 16th century, Zmijanje is organized as a district – nahija, a status which was held by the early 19th century. These historical sources also reveals that, in this period, Zmijanje was frequently changing boundaries and that held the largest territory in the first half of the 16th century, covering area between the Vrbas and Sana rivers and mountains Kozara, Dimitor and Lisina.
There are proportionally a lot of data about people’s understanding of Zmijanje, which show that this area is understood in its different territorial contexts. The first data on people’s perception of Zmijanje brings literate Petar Kočić, and based on his research Zmijanje was locate as area of a village Ratkovo as well as area of several villages on the stretch Kadina Voda – Čađavica. Furthermore, Zmijanje was understood as a much larger area bounded by the rivers Sana and Vrbas on the West and East and Kozara mountain and the source of the Pliva river in the North and South. With the problem of determining Zmijanje boundaries dealt also Milan Karanović. On the basis of anthropological and geographical studies he found that Zmijanje is area bounded by the river Vrbas and Sana in the East and West, line Banjaluka – Sanski Most in the North and the source of the Pliva river in the South.
According to recent sources Zmijanje is located in a hilly area between rivers Sana and Vrbas, which represents its eastern and western borders. With its northern part Zmijanje reaches out to City of Banja Luka, and with its southern part to the Mrkonjić Grad. It is Zmijanje in the wider sense of the term, while short-term Zmijanje is limited to the area of the village “Kadina Voda – Čađavica, with local centers in Stričići and Sitnica. This group includes the following villages: Stričići, Lusići, Dujakovci, Lokvari, Sitnica, Donje Ratkovo, Gornje Ratkovo, Stražice and Sokolovo”. By the Dayton Agreement in November of 1995, Zmijanje became a border area of the Republic of Srpska and Federation of Bosnia and Herzegovina.