Cardiopulmonary resuscitation (CPR) is an emergency procedure performed on patients during cardiac and respiratory arrest. This procedure externally activates the cardiac and respiratory systems via the delivery of chest compression and artificial ventilation. As the main purpose of CPR is to recirculate the blood flow, prediction of the myocardium behavior has great importance. This prediction allows us to have a better understanding of the needed force to recirculate blood without hurting the heart. Finite element method offer the possibility of noninvasive quantification of myocardial deformation. This method is attractive to use for the assessment of myocardial function. To investigate the behavior of the heart wall, a 3D model of thoracic organs has been prepared using medical images. In this study, to simulate the behavior of different organs, Code-Aster open software is used. For every organ, the material properties are defined. The most important parameters in the study are displacement, normal stress, and Von-Mises stress in the myocardium. Using these parameters, displacement and stress distribution have been predicted. Effects of the applied force on the chest during CPR and deformation of the myocardium have been predicted by the finite element model. A linear deformation is observable for each organ during force application. Besides, the final location of the heart and ribs and also involved parameters in predicting myocardium deformation are extracted from the model simulations. This finite element model enables us to have a good vision of the deformation of the myocardium during CPR. Using this method, it is possible to predict the deformation of every part of the heart, especially right and left ventricles.