Introduction: Polish oilseed and flaxseed collection is a source of genotypes containing very high amounts of α-linolenic acid. Objective: The objective of the study is to test the seeds for the fat content and fatty acids composition in the oil pressed from the 9 tested accessions of flax (Linum usitatissimum L.). Our goal is to promote the Polish flax collection, which seeds are unique as one of the richest sources of α-linolenic acid. Methods: Assays to determine the content of fat and fatty acids composition in linseed oil were performed at the IHAR-PIB Biochemical Laboratory in Poznań. The fat content was determined by infrared analysis (calibration performed on the basis of seed sample at IHAR-PIB in Poznań) by means of a NIRS 6500 spectrophotometer with a reflection detector within the range of 400-2500 nm. The composition of fatty acids was determined by means of a method proposed by Byczyńska and Krzymański (1969), based on gas chromatography of methyl esters of fatty acids contained in linseed oil. The following varieties of flax were investigated: Tabare (INF00111), Szegedi 30 (INF00427), Olin (INF 00444), Redwood 65 (INF00523), Dufferin (INF00540), AC Mc Duff (INF00648), Alfonso Inta (INF00683), Olinette (INF00687), Royale (INF00689). Results: The content of α-linolenic acid (ALA, C18:3) in evaluated genotypes of flax ranged from 48.9 (Royale) to 59.9% (Alfonso Inta). Content of linoleic acid (LA, C18:2) in evaluated genotypes of flax ranged from 12.4 (Tabare) to 17.1% (AC Mc Duff). The content of oleic acid (OA, C18:1) of 9 accession of flax ranged from 17.1 (Alfonso Inta) to 26.7% (Royale). The content of stearic acid in evaluated genotypes of flax ranged from 2.3 (Alfonso Inta) to 5.0% (Tabare, Szegedi 30) and the content of palmitic acid ranged from 4.7 (Dufferin) to 6.0% (Olin). The content of fat ranged from 42.7 (Olin) to 52.0% (AC Mc Duff). The fatty acid ratio n-6/n-3 ranged from 0.23/1 (Tabare) to 0.32/1 (AC Mc Duff).