Selenium is an element located in group 16 of the periodic table of elements, respectively it is a member of chalcogen family. It is a metalloid, which means it has characteristics of a metal and of a non-metal. Selenium is an essential element for humans, and it is found in enzymes glutathione peroxidase and iodothyronine 5’-de-iodinase, as well as in selenoproteins P and N. Fluorescence spectrometry is a method based on fluorescence property of an atom or a molecule and it is often used for selenium determination. Since selenium does not have fluorescence property, it is necessary to add a fluorescent reagent that will give response during measurements in fluorometer. In this paper, 2,3- diaminonaphthalene (DAN) was used as a fluorescent reagent which made a complex compound with selenium, whose fluorescence intensity was measured and the mass concentration of selenium in solutions was determined. The paper is divided in several chapters. Introduction chapter is followed by literature review in which selenium and its properties are presented as well as fluorescence spectrometry and its uses. After that, experimental procedure and discussion of obtained results are presented. In the end there is a final conclusion and a list of used literature.