Cancer genetic counselling represents a very special situation of interaction between the geneticist and the counselee, marked by a number of specificities that account for its complexity. Cancer genetic counselling has multiple repercussions, such as identification of a deleterious genetic mutation associated with a high probability of developing breast and/or ovarian cancer, the implementation of preventive measures ranging from close surveillance to the decision to perform mutilating prophylactic surgical procedures, or the impact of the information on the other members of the counselee's family also concerned by the genetic risk. This chapter is based on a review of the literature that has been rapidly growing over recent years and on our clinical expertise as psycho-oncologists and geneticists. We will first present the reasons that make the information so critical. These reasons are both objective (complexity of the genetic information per se, difficulties of understanding the concept of risk) and subjective (information given to people with an emotionally charged family history and a perception of risks closely linked to their representation of cancer). At the same time, the counsellees are charged with the transmission of this information to members of their own family. We will then discuss the various modalities of communication in this setting. While unidirectional transfer of information from the geneticist to the counselee has been the preferred method in cancer genetics for a long time, a model based on patient-centered communication is more adequate in predictive medicine and allows shared decision making. In all cases, the different professionals involved in the process have to learn how to work in a performing cohesion. We also present the main guidelines on the subject and the various underlying objectives with regard to information delivery and the subject's personal experience. Although the psychological impact of genetic counselling consultations raises a number of questions, the results of preliminary studies are reassuring, demonstrating psychological benefits. However, a number of aspects concerning communication in predictive medicine remain to be investigated and improved.