The development and application of the vehicle advanced CAE (computer aided engineering) allowed the vehicle designers to considerably reduce the weight and improve the structural performance of the body. However, the current advanced CAE model can only be available in the late design phase of the vehicle when only minor changes of the structure is feasible. Despite the detailed CAE model, which requires all detailed design, the concept CAE model can be created with less need for the detailed CAD data and it can be created in the early (concept) design phase. The members and panels of the automotive body in white (BIW) are modeled and approximated using beam and shell elements. The joints properties are then obtained from the original detailed CAE model using Guyan reduction method. The automotive seat concept model is also created and added to the concept BIW model. The developed models show good correlation with corresponding advanced CAE models as well as corresponding modal tests results in low frequency range. The interaction of the seat and BIW modes, which can be the cause of a poor seat vibration, is considered as a problem for structural optimization. Optimization of the BIW and the seat structure to prevent this mode interaction is only feasible in the early design phase. Sensitivity analysis and optimization of the structure were successfully conducted on the BIW-Seat concept model. The developed NVH CAE concept model demonstrates a good method to enhance the NVH performance in early stage of design. The proposed method can be used to effectively predict and optimize the BIW structure.