It was shown that under ex situ preservation conditions, exposure to millimeter radiation with a wavelength of 5.6 mm, a power density of 6.6 mW/cm2 and an exposure time of 30 minutes to lentil seeds, as a representative of leguminous crops, leads to the greatest stimulation of germination processes. This conclusion was made based on the study of morphophysiological (germination energy and germination rate of seeds), biochemical (content of the enzyme o-IAA, sum of readily soluble proteins in seed roots) and genetic (frequency and spectrum of chromosomal aberrations in the meristem of roots) parameters of seeds and seedlings. Moreover, stimulation of the primary metabolic processes in lentil seeds and seedlings occurs when using longer exposures to millimeter radiation (30 min) on seeds than in the experiments with the seeds of grain, cereal, vegetable and industrial crops (2, 8 min). Thus, millimeter radiation can significantly improve the viability of lentil seeds during ex situ conservation, which is extremely important and necessary to maintain the gene pool of plants.