Background and Goal of the Study: Opioids are an integral part of anaesthesia, however, there is some evidence that they have a potential to interfere with postoperative quality of sleep. Only sparse data exists with regards to long-term disturbances of quality of sleep, especially for the different types of opioids available today. We aimed to investigate the long term quality of sleep after fentanyl or remifentanil-based anaesthesia in a randomised controlled trial. Methods: After approval by the Royal Perth Hospital Ethics Committee (protocol EC2010-019) and registration at the Australian and New Zealand Clinical Trials Registry (protocol ACTRN12610000362099) we performed a prospective double-blinded study. 100 patients undergoing minor orthopaedic or plastic surgery were randomized into two groups. Patients in group F received a fentanyl-, patients in group R a remifentanil based anaesthesia. Quality of sleep was assessed preoperatively, as well as three and six months postoperatively using the Pittsburgh Sleep Quality Index (PSQI). Results and Discussion: Fifty patients were allocated to each group. In the investigated population, quality of sleep at three and six months postoperatively did not show significant differences compared to preoperative values. Likewise, we did not find a significant difference in PSQI values between the fentanyl and remifentanil group at three and six months postoperatively. However, in a subgroup analysis we found that otherwise healthy patients with a low preoperative total PSQI score (<5 ("good sleepers")) suffered from a significant long-term deterioration of their sleep architecture postoperatively, when they had received remifentanil -but not fentanyl- intraoperatively. Conclusion: There is some evidence that remifentanil may cause long-term sleep disturbances in patients with a normal preoperative sleep architecture. Consequently, remifentanil should probably be avoided in these patients, whenever possible. However, further randomised trials are neccessary to confirm or refute these findings.