Radiopharmaceuticals are a special group of drugs since many of them are eventually prepared in the hospital and the nuclear medicine department is therfore responsible for meeting quality criteria such as sterility, radionuclide, radiochemical and chemical purity. In this study radiochemical purity for more than 300 preparations of three different radiopharmaceutical formulations from commercial kits were tested using instant thin layer chromatography. The formulations namely 99mTc-DTPA, 99mTc-MDP and 99mTc-MIBI were obtained from Pars Isotope Co. Several paper chromatographic systems were used in this study. The result showed that the most observed impurities were hydrolyzed reduced 99m technetium. After the preliminary study we decided to change our imaging schedule in the nuclear medicine department and the sequence of imaging was changed. Cosequently, the results showed better radiochemical purities. Our equipments for detetion of radioactivity in paper chromatography were changed, for example the old dose calibrator was replaced by a gamma camera or a more accurate dose calibrator. Also, the thin layer chromatography systems were changed to those recommended by the factory and the new results showed much better radiochemical purities