Due to the globalization in society, modern habits are having a huge impact on the increment of possible issues that the digestive system may have. Sweden, like many other countries, is dealing with a large demand for endoscopies from people who require an exhaustive control of their issues or who want to prevent a possible intestinal problem. That is why the waiting time for the patients to have an endoscopy is usually too long.When talking about healthcare, it is important to have into account that the subject to process is people and not products. Testing different solutions in order to reduce the waiting list can be complicated because it is necessary to be careful with the process and be sure that what is done is going to work. Due to the difficulty and the risk of making changes while the system is working, the best solution is the use of Discrete Event Simulation (DES), as is it proved to be helpful in the healthcare ambit.One of the key tasks of this project was to analyze the flow of patients and workers in GHP Stockholm Gastro Center. That step provided enough information to have a global understanding of the system and the processes to develop a conceptual model to simulate. Once the translated model was verified and validated, the managers and employees perspectives and bottleneck analysis of the simulation model were taken into account for the elaboration of the different what-if scenarios. The resulting proposed scenarios were tested and a comparison among the results of the translated current state model and the results of the what-if scenarios was done. After that, the possible improvements that could be done in the system were discussed and reported at the end of this project.As a general conclusion, this project shows the potential of discrete event simulation as a tool to help the decision-makers to improve the system and reach their goals. Related to that, being capable of testing new scenarios without disturbing the current behaviour of the system is safer for the clients and also saves resources, time and costs. The conclusions after testing the different what-if scenarios were that the management of the cancellations, the addition of the number of available instruments and to limit as minimum the steps of the procedures that increment the occupation time of the room are a good way to achieve the clinic aim of reducing the waiting time for the patients to have an appointment if implemented together. Nevertheless, the addition of an operational room to process the patients with the largest waiting time is the easier way to improve the system and accomplish the goal.