Renewable raw materials are generally considered as environmentally friendly. According to the Life Cycle Assessment method, this paper presents an investigation of different automotive parts based on natural fibres and plastics. During their whole life cycle, from the provision of raw materials up to their recycling, expenditures of matter, energy and emissions are compared in order to identify the ecological effects of production and the usefulness of the parts investigated. It is shown that with respect to the demand for matter and energy and to environmentally relevant emissions, a side panel consisting of natural fibres is more advantageous than the reference part consisting of ABS injection moulding. Ecological optimisation is related to a substitution of the epoxy resin hardener system. Cultivation and processing of fibre plants are ecologically harmless in comparison to the other life cycle stages. Weighing less, further ecological advantages of natural fibre parts result from energy savings during the utilisation of a car. So far, material recycling is difficult for the natural fibre composite, therefore, incineration (or deposition) is the best disposal option. Ecological effects of the boot panels are determined by construction and by materials employed. Depending on the design, also plastics can result in lighter components.