A lost intrauterine device (IUD) is an uncommon event. Recently, a new levonorgestrel-releasing intrauterine system was introduced. In view of several cases of an unusual diagnostic discrepancy in the location of a lost levonorgestrel-releasing IUD in our department, we sought to determine if the extrauterine location of lost levonorgestrel-releasing IUDs differs from that of lost copper IUDs. The medical files of all patients with a diagnosis of lost IUD who were admitted to Rabin Medical Center from 2000 to 2003 were reviewed. Fourteen women were identified, 9 with levonorgestrel-releasing IUDs and 5 with copper IUDs. In six of the nine cases of a lost levonorgestrel-releasing IUD, there was a clear discrepancy between the presumed location of the device by diagnostic evaluation and its actual location on surgical extraction. All six devices were embedded in the omentum; four were located in the upper abdomen. No such discrepancies were noted for the copper IUDs (0 vs. 66%, p < 0.05). No significant difference in peritoneal adhesions was noted between the groups (55% vs. 66%, respectively, p = 0.095). It is concluded that lost levonorgestrel-releasing IUDs are associated with a higher rate of localization errors by clinical evaluation than copper IUDs. Lost levonorgestrel-releasing IUDs might be found in the mid-upper abdomen, embedded in omentum tissue, and this area should be explored first during laparoscopy.