Cats certainly helps keep the mice away. They may not kill the mice. It is the odor of the cat that will keep the mice away. Sometimes it will depend on the cat. There are some cats that are great mousers while some cats are really lazy and they do not care if something is moving around in the kitchen. If your cat loves to chase things away it would definitely keep the mice far away from your apartment. If the cats just sit at one place you can find mice in your apartment, chances are they won't kill the mice.