Also don't expect too much 'mental stuff' from them till they are fully grown (like 4 years old) before you can do some intensive training.

At what age is a deerhound fully grown?

They are slow developers and are still very puppyish at 9-10 months or older, when many breeds would be full-grown and developed, so you can still buy a puppy and be past the worst rearing stage. However, most breeders would want to sell puppies to new homes at about 3 months of age.

How big do deerhounds get?

The average height for a Scottish Deerhound is 30 to 32 inches for a male and from 28 inches and up for a female.