To eliminate the smell of cat urine on carpet, act quickly to remove the liquid. Use a cloth or paper towel to blot until you have soaked it all up, then use a liquid on the spot, and blot again. Finally, use an odor neutralizer, says About.com.
A good liquid to use for cleaning up urine is a mild solution of water and vinegar, says About.com. WebMD also suggests using a carpet cleaner or dish detergent in the solution to remove the urine. If the smell still remains after blotting and diluting, then you need to purchase urine odor removers to neutralize the smell with enzymes and bacteria. Animal Planet also suggests using baking soda or a hydrogen peroxide mix.
If the cat urine has already dried and set in, then you need to get specialized odor removal products. In addition, the urine may have set into the carpet padding and possibly the wood underneath. You need to pull the carpet up and treat the padding and the wood. In some cases, according to About.com, you may want to replace the carpet.
Since cats frequently urinate in the same spot, you want to make sure that there is no remaining smell. Using a pheromone product to deter felines is recommended by WebMD to prevent further issues.