Fluormisonidazole (FMISO) performs a compound from the group of nitroimidazoles which has also been extensively investigated in the past as hypoxic cell sensitizer. It was found that FMISO accumulates by simple diffusion in hypoxic tissue in proportion to cell hypoxia. The tissue distribution of FMISO labelled by 18F positron emitter can be detected using a PET camera. This makes it suitable to monitor the degree of tumor accumulation, including pharmacokinetics and pharmacodynamics, following intravenous administration of [18F]FMISO. For the first time, [18F]FMISO was designed as a positron radiopharmaceutical to monitor tumor hypoxia with PET in 1984. Subsequently, [18F]FMISO was repeatedly tested in in vitro studies on tumor tissues with various types of tumor cells and it was shown that decreasing accumulation [18F]FMISO is related to an increase in oxygen concentration.