Hi Janet, I take it that you already have the 18-270. The 18-270 is quite a different lens and more of a general purpose lens whereas the 70-300mm is more specialised. I have a Nikon 18-200mm as well as the 70-300mm. There is quite a bit of overlap but I use the two lenses for different purposes. Your 18-270 will cover almost all of the range the 70-300mm offers but it will depend on the purpose you have in mind.