The available literature provides scant information on the ranges of variation in the physical parameters of seeds of most forest shrubs, and on their relationships. Such data are needed for designing and modelling seed cleaning and sorting processes. Terminal velocity, thickness, width, length, mass and angles of external friction were determined for seeds of four juniper species (Chinese juniper, common juniper, Rocky Mountain juniper and Virginian juniper). Those parameters were used to calculate indicators that characterise the relationships between seed mass and dimensions. The results of measurements and calculations were analysed statistically by analysis of variance, correlation analysis and linear regression analysis. The average values of the analyzed properties of seeds remained within the following ranges: terminal velocity – from 6.99 to 9.51 m s–1, thickness – from 1.72 to 2.56 mm, width – from 2.23 to 3.28 mm, length – from 3.40 to 4.60 mm, angle of external friction – from 26.61 to 34.18°, mass – from 6.93 to 19.56 mg. Seed mass was most correlated with the remaining parameters, whereas the angle of external friction and density were the least correlated with the remaining properties. The highest values of the correlation coefficient and equations with the highest values of the coefficient of determination were noted for the relationships between seed mass and terminal velocity (Chinese and Virginian junipers), and seed mass and thickness (common and Rocky Mountain junipers). Juniper seeds can be effectively sorted with the use of mesh sieves with round openings with the following diameters: Virginian juniper – 1.5 and 1.75 mm, common juniper – 1.75 and 2.0 mm, Chinese juniper – 2.0 and 2.5 mm, Rocky Mountain juniper – 2.25 and 2.75 mm.