The synthesis of Tc-99m-labeled, modified RNA is reported. This new class of radiopharmaceuticals is of potential interest as target specific imaging agents. The preparation of N3S-RNA was achieved by coupling protected MAG2-units to amino modified ON's. The N3S-RNA was Tc-99m-labeled with 90-95% radiochemical yield and specific activities of 37MBq/nmol leading to 1:1-Tc-99m-N3S-aptamers.