Earth Resources Technology Satellites Program is the oldest program of the United States of America to monitor the surface of the Earth for environmental purposes. It was launched in 1972, later being renamed in Landsat. The task of this work is to process a database of satellite images from scanners TM, ETM + and OLI for the territory of the Slovak Republic and partial pre-processing of the images to enable their easier operational use in research activities. Presenting examples of deriving some characteristics of vegetation, the work also documents the possibilities of direct use of the remote sensed image data in forestry.