Surgery is a treatment that can achieve a very dramatic effect, but any surgery can lead to complications. Therefore, in order to perform safe operation, proper evaluation of the lesion should be performed before surgery and it is necessary to predict complications that may occur in each operation and prepare for preventing it. In general, complications that can occur after surgery include persistent bleeding, hematoma, secondary infection, and necrosis of the surgical site. We report three cases in which complications occurred after the residents performed the surgry. These cases are examples of common complications that we may encounter during surgery and we will look at what we could do to prevent complications.