Great question! ThermiTight uses RF energy beneath the skin (via a very thin thermistor) and can effectively tighten, tone, and contour using access points that are so tiny that they close on their own. The treatment is usually done once and requires injection of numbing solution prior to treatment.ThermiSmooth, on the other hand, uses RF energy externally to perform the same treatment. The process usually involves anywhere from 3-6 treatments each spaced a few weeks apart and there is ZERO downtime. Which treatment is best for you is tough to say and really requires consultation with a physician who has experience using both treatments. I would encourage you to check out the ThermiRF website to find a trained/experienced provider in your area. I hope that helps!