Black cormorants, Phalacrocorax carbo sinensis (the breast muscles and liver) originating from the colony near Katy Rybackie on the south coast of the Gulf of Gdańsk, Baltic Sea, were collected in 1992 and analysed for polychlorinated naphthalenes. PCNs were determined employing a multi-residue procedure including a non-destructive wide-bore open-tube extraction step, cleanup using semipermeable polyethylene membrane, HPLC fractionation of planar compounds on activated carbon column and final separation and identification and quantification with HRGC/HRMS. Tetra- to hepta-CNs were found in all samples examined, and penta- and next tetra-CNs were dominating homologue groups. Dominating members in the fingerprint of PCNs in black cormorants were 1,3,5,7-T4CN (no. 42); 1,2,3,5,7-/1,2,4,6,7-P5CN (no. 52/60); 1,2,4,6,8-P5CN (no. 61); 1,2,3,4,6,7-/1,2,3,5,6,7-H6CN (no. 66/67); 1,2,4,6-/1,2,4,7-/1,2,5,7-T4CN (no. 33/34); 1,2,4,5,7-P5CN (no. 58); and 1,2,4,7,8-P5CN (no. 62). When related to potential food items, black cormorants biomagnify in their body many PCNs and the congeners no. 42 and 66/67 show highest biomagnification factor (BMF) values.