The levels of 22 perfluorinated alkyl substances (PFASs) were examined in the livers of polar bears (PB) from Southern Hudson Bay (SHB) and Western Hudson Bay (WHB) and in the livers and adipose tissues of East Greenland (EG) PB and ringed seals (RS), all harvested in recent years. EG PB livers contained greater concentrations of ΣPFAS than SHB and WHB bears, while having greater proportions of perfluorooctane sulfonic acid (PFOS). ΣPFAS concentrations in EG PB were greater than in RS both in liver and in adipose, while no PFOS was detected in RS blubber. The biotransformation of N-Ethyl-perfluorooctane sulfonamide was significant for high enzymatic activity PB, while FOSA formation was not significant for low enzymatic activity RS. This thesis underlined the necessity to study the fate of PFASs in the Arctic marine foodweb, and the importance of short-chained PFASs and precursors when establishing PFAS exposure and levels.