Evidence supporting the effects of mergers in healthcare markets on quality is mixed. In this study we exploit a government policy in NSW that imposed mergers on area health services ( AHSs) to evaluate the effects of the merger on patient waiting times, an indicator of quality. We focus on the specific question of whether the merger had a larger impact on worse-performing AHSs. Our results show heterogeneous impacts, reducing waiting times for relatively urgent public patients but further delaying non-urgent patients. In addition, we find the merger reduced the waiting time gap between public and private patients.