Northern fulmars are pelagic seabirds known to ingest plastic, but so far most of the knowledge is on the physical characteristics of the plastic. However, plastic is a catch-all for many different types of polymers and we wanted to investigate what kinds of polymers the northern fulmars are ingesting. We did this by Fourier-transform infrared spectroscopy and found that both northern fulmars from the Faroe Islands and north-east Greenland had ingested mostly plastic made of polyethylene, followed by polypropylene and polystyrene. There were differences in the physical type of plastic ingested; fulmars from the Faroe Islands had ingested significantly more pellets compared to fulmars from NE Greenland. Thus, the physical, not polymer, composition of plastics appears to be most relevant in assessing regional differences of ingested plastic by fulmars.