Most surgical procedures in breast plastic surgery are either reconstructive procedures following oncologic interventions (tumorectomy, quadrantectomy, mastectomy ...) or aesthetic ones, both augmentation and reduction. With current techniques, the results of such procedures cannot be fully guaranteed. Usually, surgical planning is based on a photographic and anthropometric study of the breast only. Among others, one of the difficulties that the plastic surgeons have is the noticeable change of the breast shape with the position of the patient. Thus, it is more and more necessary to plan a presurgical methodology to help the plastic surgeon and guarantee the patient a successful result of the intervention. In order to establish a reliable simulation method that could predict a patient-specific outcome after breast surgery, this study started trying to correlate spatial features of the breast between lying and standing up positions. A biomechanical model of breast was proposed and implemented into a finite element context to predict deformations, and from these the breast shape in different positions. The resulting shapes were compared with multimodal images, whereas the breast surface displacements were compared with manually identified landmarks and 3D scanner images. From the results, it can be concluded that the model hereby presented reasonably approximates breast response to gravity forces, therefore providing accurate and useful information to the surgeon planning such surgical procedures.