In this letter, we propose a mechanism which may cause a strong absorption of terahertz (THz) electromagnetic radiation in AlGaAs/GaAs-based two-dimensional semiconductor systems. In such systems, the rate of electronic transitions via hot electrons interacting with impurities and phonons is on the scale of 1012 s-1 so that the THz radiation will modify strongly the processes of electron momentum and energy relaxation and, consequently, a resonant absorption of the THz electromagnetic wave may occur. We find that in these sample systems, the absorption of the electromagnetic radiation at different frequencies can be tuned by heating the electrons to different temperatures. Our results can be used for understanding and interpreting the experimental results reported very recently. �� 1996 American Institute of Physics.