Waiting lists for elective surgery are considered a major health policy concern in most countries of the world. The most common reason to explain this phenomenon is that demand exceeds supply. Traditionally, the management of waiting lists has been focused on timeliness of medical attention. The objective of this paper is to present a waiting lists management model that includes the concepts of timeliness and justice simultaneously. We designed a prioritization method based solely on medical criteria. We developed a computer software to register patients, to prioritize and monitor the waiting lists. The system was implemented in 2013 and is currently used in all surgical specialties at a public hospital. The results show that timeliness does not suffice to manage the waiting lists for elective surgery, and therefore it should be complemented with an indicator of justice. Under this management model, hospitals should attempt to balance justice with timeliness of care and prioritize initiatives that improve both indicators at the same time. In addition, we propose using this model to manage the waiting lists of other hospital processes.