Smoking during chemotherapy for colon cancer does not affect chemotherapy, but it is not recommended. Smoking during chemotherapy for colon cancer will not affect the effect of chemotherapy. However, while killing cancer cells, chemotherapeutic drugs will also kill normal cells, leading to decreased immunity of the body after chemotherapy, etc. In addition, smoking is easy to cause coughing, and once coughing is serious, it may cause mucous membrane damage, such as coughing up blood, sputum with blood in it, and so on. Therefore, smoking is not recommended during chemotherapy. Moreover, cigarettes themselves already contain a large amount of carcinogenic or toxic substances, and smoking may promote the growth of cancer cells, leading to the deterioration of the condition. Smoking is not conducive to health, and colon cancer patients are advised to quit smoking as early as possible.