I had a double mastectomy. They thought my cancer was only in the right breast but after the surgery they found it in the left as well. I also had radiation so I had to wait a year until I could finish my reconstruction. If you don't need radiation the tissue expanders and then the implants go quicker. If you do both sides you won't be wondering all the time if it will show up there too. It will also make it easier for the plastic surgeon to match them.