Many people assume that when choosing a pet for the household, they have to commit to either cats or dogs -- that they can't have both. This assumption is wrong.
Although cats and dogs do have very different characteristics and personalities, the possibility of the two getting along very much exists.
However, this may be easier when introducing a dog to a kitten or a cat to a puppy (or even a kitten to a puppy) -- this being because one (or both) won't know anything of the other and grow up with this other creature already in their life. As opposed to introducing a grown cat and grown dog together, which is a lot harder (but still very achievable, speaking from personal experience).
Getting the two to become friends may be tricky at first and take a lot of patience before it actually happens but it is very much worth it. The cuteness overload from seeing a cat and a dog cuddle or just simply hang out together is overwhelming.