If you are talking about cat chow, I have had negative experience.
Many of them are extremely high in fiber and if your cat doesn't drink
enough water, it can cause blockages - I am convinced this is what
happend to my cat - his stools became very hard and difficult to pass
and his hairballs became entangled in the stools.

I now feed a different chow (high protein) and feed abundant canned
food as well, and my cat has recovered for the most part.

-L.

I'm having good  luck with Science diet's hairball food. I use the dry
and can. (I have 2 cats, one on RX diet,the one getting the science
diet is NOT on RX food) Both my cats are longhaired