Welcome to the forum, Phoebe. Sorry to hear your cat doesn't like it's litterbox. You could try to change the litter in it or if you have one without a "roof" try one with, or the opposite if that's the case. Even try to move the box just a tiny bit might help. Cats are particular in many ways and they want it their way and no way.
If the cat is peeing in the same area in one room all the time, try to put a bowl of water or food there. Cat's doesn't like to do their bathroom stuff where they eat. But then it might just find another place, so you have to sort out the litterbox problem first and see if you can find a better location for it (more secluded maybe) or change the style of the box, perhaps get a second box if the cat likes to do #1 in one box and do #2 in another.
Hope it gets sorted out and hope to see some pictures of your little rascal!
Kitties don't like to be messy, if they are peeing on things there is usually a reason. Cat's peeing elsewhere than the litterbox is most commonly caused by:
-urinary tract infection
-litterbox not clean enough
-dislike of scented litter
-dislike of type of litter
-dislike of depth of litter
-dislike of litterbox (lots of cats don't like covered ones)
I'd take her to the vet to have her checked for a UTI. If that's not it, make sure you scoop at least once a day, and try different litters. Take the cover off yours if it has one -- kitties often don't like having to crouch down next to their stinky poo. It's like a port o potty. Also make sure you clean the pee spots with an enzyme cleaner like Get Serious or Simple Solution or Nature's Miracle...detergents and soaps won't hide the smell from your kitty. And often kitties will re-pee in places that they have already peed in if they can still smell it.
If you can't fix it by trying these things, then try to figure out what she likes so much about the living room, and duplicate it in the litterbox.
There are lots of good "enzyme" products that thoroughly remove that unpleasant urine scent. I am more familiar with their effectiveness for dog urine (epileptic greyhound ) but I think the same products probably work for cats--Simple Solution and Foster&Smith's Dogtergent or their Cattergent products have worked well for me.
You have to really soak the urine spots with the enzyme product, blot it up, and them let the enzyme product dry. It works its magic as it drys.
Natures Miracle, works like a charm, I haven't met a pet stain yet that it wont get the odor out of, you can pick that up at just about any store with a pet section now adays!
Your first step should be to bring him into the vet.
How long has this been going on for, how often does it occur, where does it happen, and have you noticed anything else different about your cat. These are just a few questions you should ask yourself, because the doctor will also want to know.
One thing that I don't think was mentioned, make sure the litter box is LARGE, some cats hate and wont use a litter box that is too small.