Hde hH de hThe invention relates to the new asymmetrically substituted derivatives of 2 7 dihydro 3 dibenzo[]cinnoline 3 7 dione and their use as cytostatics exhibiting activity against tumor cells especially against cells with multidrug resistance (MDR). In particular the invention concerns derivatives of 2 7 dihydro 3dibenzo[]cinnoline 3 7 dione represented by the general formula (I).