ABSTRACT: Environmental burdens are still an important issue in Slovakia. There are dozens of sites, that are potential or confirmed environmental burdens. The accurate identification of contaminant type is an important step in exploring the extent of contamination, as well as in estimation of possible impacts on the environment and human health and consequently also the choice of the optimal decontamination method. To identify contamination by petroleum products spectrometric analyses were performed in the past. Nowadays they are supported or substituted by gas chromatography methods. This paper is focused on identification of specific petroleum product by various laboratory methods. It deals with differences that may occur when multiple different analyses are conducted on one sample and describes the degradation of petroleum products and the consequent change in their chemical properties.