In order to turn a brittle cement matrix into a ductile composite different types of man-made fibres such as steel, glass and polyvinyl alcohol are currently used as reinforcement, as well as some natural fibres. Compared to synthetic fibres, natural fibres are more easily available worldwide and they are friendlier to the environment since less energy is needed to produce them. They are also a renewable resource. In this project natural fibres from wood were chosen as reinforcement for cement-based materials. Three softwood species: larch, spruce and pine were studied. In the matrix, cement was partially replaced with other binders to achieve a low environmental-impact matrix as well as a matrix with a tensile strength compatible with the chosen wood fibre’s strength. The wood fibre-cement matrix interface was studied. This thesis contributes to a better understanding of its properties. A lightweight cement-based composite reinforced with pine fibres was designed to exhibit deflection-hardening behaviour. This material developed multiple cracking prior to failure under bending stress. Due to this improved behaviour it can be considered for applications such as low-budget housing in countries subject to seismic risk, where ductility and low weight are desirable characteristics of the building material.