If your cat has already learned how to open the cabinet doors, you may need to take more drastic measures. One option is to put a bag of citrus peels or lemon juice inside the cabinet so the smell'll deter them. You can also try placing a bowl of water or food inside the cabinet, so they have less reason to go in there. Finally, you can try putting double-sided adhesive tape around the edges of the doors so they won't be able to get open.