When we got Monty (at age 4 yrs) his previous owners said he had never met a cat before. He just stood and stared at our cat Darwin (who is fearless) for the first couple of days. It was quite funny! I was a bit concerned at first because Darwin is so fearless, would he run if Monty tried to get him. He then followed the cat around and still does with his nose up his butt but that is about it. He is still curious but if he gets too pushy he gets slapped although he is lucky there are no claws!. He did chase him once but it was very halfhearted. My other dog does chase Darwin if he can and thinks the cat is his own personal toy. They used to play-fight but I have had to put a stop to all of that as Monty became very interested and I didn't want a pack type situation versus the cat. If you are getting a puppy, you will be able to train it. If you are getting an older dog then it will depend entirely on that dog and how he will react. We rescued a boxer before we got Monty but had to give her back because of how she used to track the cat all the time. We could never trust her or relax and she was a whole lot faster than Monty (or us!) ever thought of being! It broke our hearts as she was a lovely girl but Darwin was here first. She is now in a cat free home. Good luck!