We have a 23 (?) pound big....male cat who was about 7 when we got our puppy. We were not sure what he would do, but he pretty much ignored the puppy. I think they would have become great friends when Sophie (our puppy) suddenly got very sick after we had her for only three weeks. She wanted to lay down with the cat and be comforted, but he wouldn't have it. Today, after 5 1/2 years, Sophie, our Yorkie is the boss. She bites at his heals and makes him go where she wants him. She makes him jump up on the chair or onto the platform where we have his food bowl. She is "in charge" of what the cat does. I have seen him have a stand-off with my daughter's dog (a beagle/spaniel cross), but she has never been mean to Sophie. Sophie on the other hand will attack the cat if she thinks the cat is getting our attention. In the evening, they both sleep on the bed, the cat on the actual bed, and the dog on top of the pillows.