Polybrominated diphenyl ethers (PBDEs) are persistent and lipophilic compounds used as flame retardants in electronic equipment, plastic material and synthetic fibbers among other things. The PBDEs are mainly used as Deca-BDE and Bromokal 70-5DE, a mixture of tetra-, penta- and hexa-BDE. Due to its chemical and physical properties PBDEs, especially TeBDEs, tend to bioaccumulate. PBDEs were first reported in sediments in USA, and in fish from a Swedish river. More recently PBDEs have also been reported in seals, birds, mussels, whales and humans. In this study an SFE-method for rapid analysis of PBDEs in marine mammals was developed. This method was used to determinate the concentrations of these environmental pollutants in Pilot Whale samples caught in the Faroe Islands, Beluga Whales from the Arctic and Polar Bears from Svalbard. Using this method several PBDEs were analysed in the different species. In addition methoxylated PBDEs (Me-O-PBDE) were identified by interpretation of the different mass spectra’s. Of the 209 theoretical possible congeners only a few PBDE seem to accumulate in the environment. Accumulation of PBDE is related to the different chemical properties of the molecule. With the help of multivariate characterisation of a compound class using semi-empirical molecular orbital calculations, literature data and actual experimental measurements, the behaviour of PBDE in the environment can be modelled and predicted. Such models are essential in order to gain more insight in the behaviour of PBDE in the environment.