The aim of this work was focused on monitoring the sedimentation of non-spherical particles in High-Performance Concrete (HPC) mixtures. HPC mixtures has better mechanical-physical properties (high strength, high density high workability, low permeability and high resistance to chemical attack) than ordinary concrete. HPC is composed of fine aggregate, silica fume, slag, cement, water and superplasticizer. To achieve higher tensile strengths, the fine-grained matrix is reinforced with the reinforcement – fibres. The final mechanical properties of HPC depends not only on the mixture composition but also on the type of used fibres and their homogenization in mixture. Four concrete mixtures with same component proportion was chosen for experiments. Water was the only one component, that was changing in mixture recipes. Steel fibres with a ratio of d/l = 0.3/20 were used as reinforcement. The fibre volume in mixture was 1.5 %. The test specimen (cube 120 x 120 mm) was made from each HPC mixture. After 28 days of hardening, the test specimen was cut in the middle and prepared for the microscopy analysis. The stereomicroscope Olympus SZ61 and the optical microscope Nikon Eclipse ME600 with software NIS-Elements was used for evaluation of the fibre distribution in the test specimen. The entire cross-section from the surface to the bottom of the test specimen was monitored. It was obtained, that the concentration of the fibres increases with distance from the surface to the bottom of the HPC structure and this non-homogeneity increases with higher water dosage. The dependence of sedimentation of fibres on composition of HPC mixtures can be used for evaluation and optimization of final mechanical properties of the HPC structures.