Hi ILUVMYCATS and welcome to Pet Talk! Yes, what wayne mentioned are all important things to check first. UTI can be a very frustrating thing (for cat AND owner), and having a UTI boy myself, I can relate. Chances are, since your cat has been diagnosed with UTI, it could be that he is associating the litter box with the pain of UTI, so he is eliminating outside of the box hoping that the pain won't be there. The trouble is once that happens...those spots need to be cleaned with an enzymatic cleaner since the amonia of cat urine is so strong that a cat will smell it, and will continue to go there. If the cleaning doesn't curb the smell, try placing little bowls of food where the cat has eliminated...since cats usually don't like to eat where they eliminate.
Also, you may need to reacclimate your cat to its litter box if he has been avoiding it. Like wayne mentioned, keep it spotless! Our UTI boy is very picky (and I mean VERY picky!) about litterbox cleanliness. Maybe even put out an extra box, so he has multiple options.
Was this a recent diagnoses? Is your cat currently on antibiotics??
I sure hope some of the info helps, and do let us know some more background about your cat, so we may be able to give a better assessment. I know this can be a frustrating thing, so hang in there and give your baby some extra luvins!!
**hugs**

Again, welcome to Pet Talk!