Mobile phones' radiation influence on a homogenous human model located inside a car is studied in this research. One of the novelty of proposed research is earth surface influence consideration under the car on EM field formation inside it. The inner field and its amplification by the car's walls that in some cases act like a resonator are studied. The problem was solved numerically using the Method of Auxiliary Sources. Numerical simulations were carried out at the 450, 900, 1800 [MHz] standard communication frequencies. Obtained results showed the presence of resonant phenomena inside the car.