In recent years, the use of fl ax fi bres to replace glass fi bres as reinforcement in polymer composites has gained popularity due to an increasing environmental concern and requirement for developing sustainable materials. Many works deal with the properties of fl ax fi bres cultivated for textile applications, which are today used for polymer reinforcement. As fi brous material from oleaginous fl ax varieties and shives is available in large quantities and not promoted, its use in composites shall be further developed in the forthcoming years. Croatia and Slovenia mainly grow oleaginous fl ax, where after the seed collecting, most of the stems remain unused, the major portion being burned in fi elds, creating environmental pollution, or being disposed by ploughing. Therefore, the aim of this study was to characterise and compare the properties of shives and technical fi bres extracted from fl ax Linum usitatissimum L., a textile variety planted in Croatia and from the Slovenian autochthonous oleaginous variety from Bela Krajina, to be used as potential reinforcement in polymer composites. The fl ax stems of the textile variety were subjected to water retting for 72 hours and the fl ax stems of the oleaginous variety were dew retted for four weeks. Dried retted stems were passed through a mechanical process of breaking and scotching, followed by heckling and combing, where the shives and fibres were separated into four groups according to their length. The characterisation of the fi brous material of both varieties was studied according to the results of optical and scanning electron microscopy, moisture regain, fi bre length, linear density and tensile strength, and according to the results of Fourier transform infrared spectroscopy and thermogravimetric analysis. Based on the analysis results, it was concluded that the properties of investigated textile and oleaginous fl ax fi brous material were comparable, as were the properties of tested fi bre length groups within the same variety; that fl ax fi bres from textile and oleaginous varieties have adequate morphological and mechanical properties, and thermal stability for reinforcing polymer matrix composites; and that fl ax shives are more appropriate for fi llers in plastics with a lower reinforcing role. As the type of fi bre reinforcement (short fi bres, roving/yarns, nonwoven or woven fabrics) is very important for polymer composite properties, based on the obtained results, fi bres can be selected for specifi c purposes. Keywords: textile fl ax, oleaginous fl ax, fi brous material, polymer composite, reinforcement