Crohn’s disease (CD for short) characteristically presents with mucosal ulcers that can involve the entire GI tract, but most commonly the distal ileum and colon. Therefore, colonoscopy has a very important role in the initial diagnosis of CD. In diagnosed cases, colonoscopy can be used to evaluate the efficacy of drug therapy and may have some predictive value for the patient’s future condition. We address this topic from the following three questions. The first question: Is the relief of clinical symptoms accompanied by an improvement of the endoscopic lesion? The answer is not necessarily! In clinical practice, we often observe that some patients have complete remission of clinical symptoms, but a review of the colonoscopy reveals no significant change in the intestinal lesions from before treatment. Scientific studies have also found that after treatment with some drugs: for example, salazosulfapyridine, 5-aminosalicylic acid, antibiotics or glucocorticoids, the patient’s symptoms can be effectively controlled, but the lesions on the colonoscopy are not significantly better. But this is not always the case! There are also drugs such as azathioprine and biologic agents that, after treatment, have resulted in some patients not only in clinical symptom relief, but also in complete healing of the previously diseased ulcer on colonoscopy. Because of these findings, the goal of CD treatment has gradually changed from “symptom relief and recurrence prevention” to “symptom relief, induction and maintenance of mucosal healing, and recurrence prevention”. Second question: What is the impact of drug therapy to induce mucosal healing on the long-term course of the patient? In 2004, a very famous study conducted abroad used a new biologic agent —- to treat CD and observed the efficacy of the treatment, and found that the mucosal healing rate was higher in patients treated regularly with infliximab for 1 year, and the subsequent hospitalization and surgery rates were significantly lower in these patients. The rate of subsequent hospitalization and surgery was significantly lower in these patients. A final question: can patients stop the drug after maintaining mucosal healing and is the recurrence rate reduced after discontinuation? It is important to clarify that, to date, CD is still a disease that cannot be completely cured, and even if some patients have complete healing of the endoscopic lesion after treatment, it does not mean that the disease is cured and treatment can be stopped. A foreign study reported data on the discontinuation of CD after the application of infliximab treatment. They found that disease recurrence after discontinuation of treatment in patients who achieved mucosal healing did occur later than in patients who did not achieve mucosal healing, but recurrence occurred in most patients once the drug was discontinued regardless of the presence or absence of mucosal lesions. In conclusion, endoscopy can help clinicians determine the severity of the disease and the efficacy of drug therapy. Long-term mucosal healing has the potential to improve the long-term prognosis of patients. However, treatment must be maintained after mucosal healing, otherwise most patients are still prone to recurrence.