Аннотация:Absorbed dose distributions in hollow organs media were modeled for photon and alpha-radiation of different energies with the help of Geant4 toolkit. In case of photon radiation the created model showed the results that were in good agreement with the standard. This model was also used to analyze the energy absorbed fractions from alpha radiation of the radionuclide 211At. It was assumed that for organs with complicated geometry (hollow organs, for example) only a thin layer on the boundary contributes to the absorbed dose. The analysis showed that in case of alpha radiation more sophisticated model of activity distribution should be used in order not to underestimate the dose.