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The inflow of solar radiation to the active surface is among the crucial factors determining its radiation balance and thus the climate conditions. Due to limited research and a multitude of surfaces, the determination of the spatial distribution of solar radiation on the basis of in situ research is hampered. Therefore actinometrical models are used to calculate the value of solar irradiance with reference to digital elevation models. Two actinometrical models were described: r.sun implemented in the GRASS GIS software and the Area Solar Radiation (ARS) provided in the ArcMap program, a part of the ArcGIS package. A digital elevation model of the East Carpathian Mountains in Romania was used as entry data for the above described models and a comparative analysis of the following characteristics was performed: total solar irradiance, direct irradiance, diffused irradiance and direct daylight duration. It was determined that despite the fact that both actinometrical models show different values of solar irradiance for the same area, they reflect similar spatial distributions. While both models are deemed valid tools for calculating solar radiation in mountainous areas, elementary knowledge of the tools is a must in order to use the results in an informed and responsible way. 7 77 97 7 Badania Fizjograficzne