Results of acoustical simulation of a vehicle with seats is presented in this paper, providing some basic understanding how the geometry of the seats as well as the acoustical properties of the seat material can affect the acoustical behavior of the interior. Both a finite element model and a boundary element acoustical model for a minivan with seats are generated. The influence of a change of seat geometry on modes and response is calculated first. In addition, the effects of acoustical properties of the seat material, i.e. airflow resistivity, on absorption respectively boom reduction is investigated.The simulation results have shown that the geometry of the seats has to be modeled quite accurately in order to achieve good simulation results. It has been found that rather small changes of the seat model may cause noticeable changes in modal behavior and acoustical response. Moreover, it is demonstrated how the airflow resistance of the seat material can have a large effect on the acoustical response at low frequency in a vehicle, especially by modifying the natural frequencies and loss factors of longitudinal modes.Following these simulation results, a vehicle has been tested with seats made of different materials and also with different geometrical modifications. The test results are in good agreement with the simulation results.