I have a 9 year old male ShiTzu and plan to add a Yorki puppy to our family in the spring. Male or Female?

to prevent any potential problems, female.
Make sure both are fixed, for their own health, as well as to prevent unwanted puppies.
adult male dogs get along better with females.

Well,females are calmer. If you have a old dog , don't choose a jumpy dog , it will tire the old thing out !

I would get a female. If you get a male, the pup would try to show dominance and it might be very stressful for the Shih Tzu.

Younger female. It will cause less dominance problems.

Remember to watch the puppy for being to aggressive with an older dog who might not like hours of fun like the puppy will want. Your older dog will correct the puppy when he has had enough, but you might want to be there to control that for him.

defo female hun. adult males will accept a female more readily than a male (although this depends on your dogs nature) but have your male neutered, before your puppy has had her first season. although some vets will spay the female without having had a season. its always a good idea to let the dogs meet, before you bring the new puppy to your home. sometimes they will chose each other, making your job a lot easier.

be very careful when adding anything to a shitzu's house they are a very dominating breed escpecially when you add another animal they may not like that idea, and become aggressive, especially at his age, i know from experince i had a shitzu female and she didnt like us adding anything into her area

Female! Getting another male could make your 9 year old feel like he's "stepping on his turf" and problems could arise. He'll be much more accepting of a female. But I would suggest spaying her or fixing both because the mix breed of those two dogs would not be a good combination health wise.

I would go with the female since you already have a male. Males always are in competition and fight a lot more with each other than with females.

Generally, a male and female will get along best. But if your shih tzu is neutered, laid back and dog friendly, another male would be fine too, especially if your getting him neutered.

hm..male. the ShiTzu would make a great father for the puppy since he hasnt had one in a long time. older males tend to protect younger males as if they were father and son.