Modular lightweight design offers potentials for realizing cost-effective, customer specific and energy efficient products.However, modularization to allow multiple use of modules often implies oversizing of modules. Therefore, modularlightweight design is contradictory to the core idea of lightweight design. The interdisciplinary development of mechatronicsystems increases the need for trade-offs between lightweight design and modularization, since all disciplines involvedhave a direct influence on the definition of the product architecture. These trade-offs lead to a highly iterative approach.To reduce iteration loops and shorten product development time, the requirements are transferred into a targetsystem and decision criteria between the modularization of a mechatronic system and the potentials of lightweight designare derived. Validation is based on an Unmanned Aerial Vehicle (UAV). The results are used to draw conclusions regardingthe integration of modular lightweight design into the product development procedure according to VDI 2206.