<p>There is a basic contradiction in modern healthcare: while there is an urgent need for more resources to provide documented effective care in many health systems, the same systems provide extensive services that are reported to have little or no effect on people's health. This induces long wait times, delayed diagnoses and treatments, poorer prognosis, and worse outcomes. That is, a wide range of studies have demonstrated health care systems to provide large volumes of low-value services while not being able to provide much needed high-value services. This contradiction between simultaneous overuse and underuse can be analysed in a paradox framework. Moreover, identifying the drivers of overuse and underuse can help us develop strategies to curb the problem, its implications, and free resources for reducing underuse. Hence, resolving the overuse-underuse paradox is crucial for the viability of healthcare systems: for the safety, quality, effectiveness, efficiency, and sustainability of care. </p>