Quantitative values are necessary for modelling mechanical properties. For fibre reinforced polymers, fibre orientation, fibre length, fibre fraction and fibre shape are important features. X-ray computed tomography (CT) was used to determine these features for special types of fibres. Long glass fibres, Cellulose fibres and polymer fibres were analysed. They exhibit the feature of bending. Single fibre characterisation methods that were developed for straight fibres were extended in order to achieve accurate quantitative results also for bent fibres. The qualitative analysis of CT data showed principle differences between glass and Cellulose/polymer fibres. While glass fibres have smooth surface and tend to be straight, Cellulose and polymer fibres have rough surface and bend severely. The cross section of glass fibres is circular and of Cellulose and polymer fibres elliptical. This ribbon like structure is often twisted along the fibre axis. Quantitate features for modelling were extracted by applying a Poly Inclusion model. The length was determined by summing up intermediate Euclidian distances. This work shows the possibilities of quantitative single fibre characterization for bent fibres by means of CT. The optimizations lead to applicability for modelling mechanical and physical properties of this type of composites.