Waiting times for elective (non-emergency) treatments are a key health policy concern in several OECD countries. This study describes common measures on waiting times across OECD countries from administrative data. It focuses on common elective procedures, like hip and knee replacement, and cataract surgery, where waiting times are notoriously long. It provides comparative data on waiting times across twelve OECD countries and presents trends in waiting times in the last decade. Waiting times appear to be low in the Netherlands and Denmark. In the last decade the United Kingdom (in particular England), Finland and the Netherlands have witnessed large reductions in waiting times which can be attributed to a range of policy initiatives, including higher spending, waiting-times target schemes, and incentive mechanisms which reward higher levels of activity. The negative trend in these countries has however halted in recent years and in some cases reverted. The analysis also emphasizes systematic differences across different waiting-time measures, in particular between the distribution of waiting times of patients treated versus the one of patients on the list. For example, the mean waiting time of patients on the list is generally higher than the mean waiting time of patients treated though we can find examples of the opposite. Mean waiting times are systematically higher than median waiting times and the difference can be quantitatively large.