This book seeks to address the emotional impact and emerging emotions when the diagnosis of cancer disease arises. Based on Lazarus's concept of emotion, aiming to determine the emotions triggered by the diagnosis, a descriptive study of a qualitative nature was developed. The results of the study allowed us to conclude that, in the face of the diagnosis of oncological disease, the emotions of fear and anger emerge. To cope with the disease situation, the study participants presented the following coping strategies: emotional/cognitive self-control, confrontational, distancing, seeking emotional/informative social support, avoidance/avoidance and positive reappraisal. It is emphasised that, although emerging emotions are considered in the literature as negative, they have a very important adaptive potential. Understanding the emotions and coping strategies inherent to a cancer diagnosis seems to favour skills that enhance the effectiveness of a therapeutic relationship that promotes the patient's emotional well-being and facilitates their adaptation process.