Global climatic changes cause changes of landscapes and their particular components. The mountain altitudinal treeline in the tundra – taiga transition zone is one of features most sensitive to these changes. The dynamics of its altitudinal position represents a great interest. In this article we suggest a technique of how to process remotely sensed images acquired at different times by different sensors for the definition of treeline position. For case study of the Khibiny mountains we compare the altitudinal treeline position in archived aerial photographs and modern satellite very-high resolution imagery. We have considered two dataset options: in the presence of a detailed DEM and in the absence of comprehensive elevation data and have assessed the accuracy of results for both options.