A new methodology for designing hybrid assembly lines including Remote Laser Welding (RLW) and Resistance Spot Welding (RSW) stations is presented. It is based on two tools, the “Assembly Process Concept Generator” and the “System Configuration Module” which can be executed independently or within an integrated software platform. The “Assembly Process Concept Generator” allows to perform a preliminary process estimation providing to the user an integrated environment based on a GUI (Graphical User Interface), where assembly resources, operation sheet and KPIs can be managed and checked in the same window. The “System Configuration Module” provides a modeling and optimization environment where several alternative system configurations can be tested before implementation by exploiting the features of a fast performance evaluation module, based on approximate analytical methods. The description of the two tools and the implementation of an industrial automotive test case, part of the EU funded project RLW Navigator, are described.