This thesis is a research dealing with the development of high performance cementitious materials with the addition of waste carbon fibres from local sources, which is a by-product of the production of high-performance construction textiles used for various composite systems. In order for waste fibres to be used on a larger scale, as an additive to construction materials, their properties and behaviour in cement composites must be thoroughly researched and tested. For this purpose, tests on volume stability, in particular autogenous shrinkage and drying shrinkage, were carried out in this thesis on cement mortar samples with the addition of 6 and 12 mm long waste carbon fibres, which were dosed in volume fractions of 0.5 %, 1 % and 2 %. A reference mixture without fibres and mixtures with 1% of factory fibres of 6 and 12 mm length were also used for comparison. The thesis describes the problem and cause of autogenous shrinkage and drying shrinkage and explains the mechanisms of fibre influence on cement mortar in terms of volume deformations and influence on moisture exchange with the environment. The experimental part describes the procedure for preparing the samples and the tests carried out in the fresh and hardened state. The test results show that there is a positive influence of waste carbon fibres but also a critical amount of fibres that can be used because when exceeded, this leads to poor workability in the fresh state and unsatisfactory behaviour of the samples in terms of shrinkage. The identification of such behaviour is crucial in order to find solutions and for develop new technological processes in the future.