Fish (herring, cod, eelpout, round goby, flounder, perch, lamprey, pikeperch, sand eel and lesser sand eel) caught in the Gulf of Gdańsk in 1992 did contained the residues of penta- (PCBz) and hexachlorobenzene (HCBz) in concentrations from 0,09 to 0,75 and from 0.36 to 3.7 ng/g wet weight (3.3-14 and 6.5-41 ng/g lipid weight), respectively. Both compounds were identified and quantified using capillary gas chromatography and low resolution mass spectrometry (HRGC/LRMS) after a non-destructive extraction an clean-up step with a semipermeable polyethylene membrane and further fractionation on the Florisil column. A higher HCBz/PCBz ratio indicated in some species of fish caught under city of Gdynia when compared to the specimens caught close to the city of Gdańsk did indicated an existence of a slight local source of pollution with HCBz in the area of the seaport of the city of Gdynia.