The aim of study was to determine the content of basic nutrients, the level of fatty acids, tocopherols, xanthophyll, and lycopene, and the total phenolic content in camelina (Camelina sativa L. Crantz) (Cs), sunflower (Helianthus L.) (Ha), and flax (Linum L.) (Lu) seeds. The seeds were either raw or subjected to processing, i.e. boiling, micronization, or microwave roasting. The basic chemical composition was established and the fatty acid composition as well as the content of tocopherol (α, β, γ, δ, total), β-carotenoids, xanthophyll, lycopene, and total phenolics were determined in the analyzed oil seeds. The analyzed oil seeds are a rich source of protein and PUFAs as well as α-tocopherols (Ha) and γ-tocopherols (Cs, Lu), xanthophyll, and phenolics One portion of seeds covered from 746/513 (Cs) to as much as 1209/813% (Lu) (female/male) of the ALA daily intake. The AI value in the processed seeds increased (P < 0.05) and the values of H/H and HC declined (P < 0.05). The oil seed processing resulted in loss of most nutrients and bioactive constituents and appearance of some amounts of trans isomers, especially in the microwave roasted seeds (0.99–1.79 g/100 g crude lipid). The phenolic content decreased in the boiled seeds (Ha: 1301; Cs: 578.3, and Lu: 62.75 mg/100 g).