Erik- false positive are indeed something discussed often when talking about PET scans. Reports of rates as high as 20%. But it is not the technology that is at fault here, it is the general nature of what a PET finds. If you have read about them on the main body of the web site, you know that they do not find cancer, they find cells where metabolic activity is high.... measured by the above average burning of sugars in the cells. Certainly malignant cells have a higher metabolic activity than normal cells. But many things besides cancer can cause this to take place, and not all those are life-threatening issues. So a positive PET doesn't necessary mean you have a met or recurrence of cancer. As Gary has mentioned here before, the current gold standard for a more definitive read is a PET/CT fusion scan. Things that show up on the PET but not the overlaying CT are unlikely to be cancer. The best of both technologies yields a much better result.