Superior mechanical properties, low density and a unique appearance have made carbon fibre rein-forced polymers (CFRP) one of the best-known lightweight design materials in automotive engineering. Nevertheless, CFRP has not yet been able to establish itself across the board. Reasons include the high price, the complex design and the lack of experience of most design engineers in handling this material. In this thesis, a methodology was developed to support inexperienced design engineers (with regard to CFRP design) in identifying lightweight potential and to develop innovative concepts that offer the greatest added value for the full vehicle. A focus was on the integration of both components and functions across the borders between interior and exterior to generate additional lightweight potential. For this purpose, the approaches of functional lightweight design, material lightweight design and shape lightweight design were used under the main aspects of system lightweight design. In order to reduce complexity, the three parameters of function, geometry and material were optimised independently of each other using different design tools. The developed methodology enables the quick and easy selection of the right design tools. Whenever no adequate tool could be identified in the state of the art, new tools were developed or existing ones adapted. Finally, the methodology was exemplarily applied to the subsystem "door" and presented with two concepts. The developed methodology allows the rapid assessment of lightweight potential and the identification of the best concepts despite the strong limitations of the automotive industry (cost pressure, carry-over parts, innovation pressure, etc.).