AbstractIn this paper, the impact of mean size of anisometric hemp shives particles (length) on compressive strength and other parameters of lightweight composites is studied. Sample of hemp shive with a wide lengths distribution (8 – 0.2mm; mean length: 33.7mm) and two separated fractions (< 4mm and 4-8mm) with mean length of particles 7.3mm and 27.7mm were used in the experiments. Composites based on MgO-cement as a binder with a constant ratio of hemp shives (40 vol. %) were prepared. Density, compressive strength, thermal conductivity and water absorbability of composites after 28 days of hardening were tested. Effect of mean length of hemp shives slices on the above mentioned characteristics of fibrous composites was confirmed. Values of density and compressive strength of fibrous composites increase with decreasing length of hemp shive slices. The lowest value of water absorbability was recorded for composite based on fraction with short length of hemp shives slices. The impact of mean length of hemp shive slices on thermal conductivity parameter was not confirmed.