The Shih-poo may vary greatly in size depending on the variation of Poodle with which the Shih-Tzu was breed, and Poodles come in Toy, Miniature and Standard sizes. Nearly all breeders tend to use Toy and Miniature Poodles as most people want very small dogs, and as Shih-Tzus are small dogs as well, the best results usually involves the two smaller Poodles.
Like any hybrid, a Shih-Tzu's personality and appearance will depend on what it inherits from its Shih-Tzu and Poodle parents. Some Shih-poos may have more Shih-Tzu whereas others may have more Poodle — and then there will be those that get a perfect mix of both breeds. Until they are grown, however, it will not be easy to determine how much of which parent your pup will have inherited, for even those in the same litter will almost never get the same traits as the others.
Nevertheless, most Shih-poos tend to be inquisitive, highly intelligent, a wee bit stubborn but almost always happy to be a companion. They aren't barkers, for the most part, but they do make good watchdogs as they are alert. They do not make good dogs due to their small size — although they don't seem to know they are small dogs; they get their attitude from several centuries of the Shih-Tzu parent being pampered by royalty and a fearlessness from their hunter parent, the Poodle.