Dimensional characteristics of natural fibres are highly dependent on their botanical origin and extraction processes. Furthermore, their dimensions and physical properties could vary according to environmental conditions (humidity, temperature...). Advances in the development of natural fibres reinforced composites for engineering applications require a reliable prediction of their mechanical performances. From this point of view, the morphology of natural fibres should be assessed accurately so as to implement their intrinsic mechanical properties in mechanical predictive models. The dimensional measurement of natural fibres cross-section is usually based on assumptions of their sectional shape and rarely takes into account dimensional variations along their length. This study proposes a detailed dimensional analysis of various natural fibres species based on the comparison of two very different approaches: microscopic observations and an automated laser scanning technique.