Seed vigour, viability, the contents of soluble carbohydrates, total protein, albumins, and globulins, as well as seed coat structure, were analysed in yellow lupin (Lupinus luteus L.) cv. Iryd seeds stored for 20 years at -14°C, 0°C or at room temperature (approx. +20°C). Seed storage at room temperature reduced viability (to 2%) and increased seed leachate electroconductivity. Determinations of total proteins showed that protein content was significantly reduced in seeds stored at +20°C compared to the other storage regimens. Raffinose family oligosaccharides were the main soluble carbohydrates in seeds stored at 0°C and -14°C, whereas sucrose dominated in seeds stored at room temperature. Scanning electron microscopy (SEM) of seed surface and seed coat sections revealed appearance of an amorphic layer on the surface of seeds stored at room temperature (not observed in other seeds) and distinct shrinking of macrosclereid layer in seeds stored at -14°C. Macrosclereids layer in all seeds was 100 µm thick and accounted for 60% of seed coat thickness. The obtained results suggest that for long term storage of lupin seeds at 0°C is the most advisable temperature if both costs of storage and seed storability are considered.