Remotely sensed images of the Earth's surface provide information about the spatial distribution of evapotranspiration. Since the spatial resolution of evapotranspiration predictions depends on the sensor type; scaling transfer between images of different scales needs to be investigated. In this study, the Surface Energy Balance Algorithm for Land (SEBAL) was used to derive evapotranspiration maps from LandSat7 Thematic Mapper (TM) and Moderate Resolution Imaging Spectroradiometer (MODIS) images. LandSat7 has a spatial resolution of 60 m, MODIS of 1000 m in thermal band. The objectives of this study are first to validate the consistency of SEBAL algorithms for satellite images of different scales and second to investigate the effect of up- and down-scaling procedures between evapotranspiration maps derived from LandSat 7 and MODIS images. The results of this study demonstrate: (1) good agreement of SEBAL evapotranspiration estimates between LandSat 7 and MODIS images; (2) up- and down-scaled evapotranspiration maps over the Middle Rio Grande Basin are very similar to evapotranspiration maps directly derived from LandSat 7 and MODIS images.