SUMMARY. Different aspects of phytin accumulation in mature flax seeds are considered: range of variation, an impact of the environmental conditions and morphology of phytate globoids. Over a period of 2005–2009 harvest seasons the phytin concentration in flax seeds varied from 29.3 to 35.4 g/kg. Intensive rain and cool weather during seed maturation promoted phytic acid accumulation. According to the SEM, cotyledonous globoids are electron-dense spherical concretions with an average diameter of 2.3–5.6 µm. Chemical elements K, Mg, Mn, Ca and Fe were detected in the chemical composition of phytate globoids.