Come Together (Dogs and other dogs)

[littlebit]

Hi All:
I already have a large breed dog. He's gentle and loves other animals, large and small. Its my boyfriend's dog, really, but I want to add dog to the family. I want to get a Shih Tzu because I know that they are typically timid and won't pick fights with the larger dog (the way that a Min Pin would). I'm wondering, can a small breed dog and a large breed dog get along and live in harmony? I figure given the breeds, they should do fine, but I want to get some outside opinions before doing anything.