Sarcopenia is a progressive skeletal muscle disease characterized by a pathological decrease in muscle mass and function and is common in the elderly. Most cancer patients are elderly and patients may already have sarcopenia before the onset of cancer. Additionally cancer promotes muscle aging making cancer patients more susceptible to sarcopenia. Cachexia another common multifactorial syndrome in cancer patients manifests as anorexia involuntary weight loss and persistent skeletal muscle wasting which cannot be fully reversed by conventional nutritional therapy and may eventually lead to progressive functional impairment. Sarcopenia and cachexia share many similarities in their causes and characteristics. For example loss of muscle mass is a common diagnostic factor in both syndromes thus sarcopenia and cachexia are often referred to as each other in cancer patients. Therefore it is of great significance to elaborate on their characteristics and differences in cancer patients. Here we provide a comprehensive comparison of sarcopenia and cachexia in cancer patients elucidate the similarities and differences between the two diseases and provide evidence-based strategies for the management of cancer patients with sarcopenia.