It can be done, but it will almost certainly require surgery (trimming; modding lips; etc.) and cause limitations / rubbing.
Without details on what you have and what you're trying to do I can't offer more than that.
Go to Google and search this domain (customtacos.com) on "18X9" to get a listing of prior threads and posts relating to using that size wheel. That's the best way to explore what others have done (or had problems doing).
Mine are 18x9 et24 Saleen reps with 235/45-18 tires. Rear fender lips are trimmed and barely touch with a 3" drop in the rear. The fronts rub pretty hard at the top of the inner fender but not the lips as I rolled/ and pulled the fenders. I had a bj flip and stock springs with kyb stock length shocks and any hard cornering would cause the fronts to rub pretty hard.
Today I installed a set of 2015 Tacoma Pre Runner front springs with ! coil cut off and the truck rides 1-1.5 inches higher, but doesn't rub at all. Going to cut another full coil off and see where the ride height ends up. The new springs were the same length as the stocks before the cut, as is the spring diameter. However the individual coil diameter is 3mm larger and a fair amount stiffer. Will post more pics later.