Screening of nutritional status of cancer patients plays a crucial role in the perioperative management and is mandatory for the certification of oncological centers by the German Cancer Society (DKG). The available screening tools do not differentiate between muscle and adipose tissue. Recent advances in computed tomography (CT) and magnetic resonance imaging (MRI) as well as the automatic picture archiving communication system (PACS) imaging analysis by high performance reconstruction systems have recently enabled a detailed analysis of adipose tissue and muscle quality. Rapidly growing evidence shows that body composition parameters, especially reduced muscle mass, are associated with adverse outcomes in cancer patients and have been reported to negatively affect overall survival (OS), disease-free survival (DFS), toxicity associated with chemotherapy and surgical complications. In this article, we summarize the recent literature and present the clinical influence of body composition in oncological visceral diseases.