Bullmastiff Temprament :
If you are looking for a true best friend, the Bullmastiff might be for you. These large and powerful dogs make excellent companions because they are so loyal and protective. They will want to go with you everywhere, be part of everything you do, and will not do well behaviorally if they do not get the attention they crave. They are good with children and are protective of them. They are quiet dogs, but will bark loudly when they sense a threat. They are not always good with other dogs, and can show dog aggression, so it is important to socialize them early in life. They are natural guard dogs and can be territorial to a fault. While it is great that they will protect you with their life, they can also get into trouble by not allowing any other animals to trespass onto "their" property. Bullmastiffs are faithful, sensitive, intelligent, and eager to please. They are laidback (unless threatened), fearless, active, docile, spirited, and famous for the unconditional love they show their humans. They are confident and can sometimes be stubborn. Their famous flaw is their slobber. You need to be prepared to keep a slobber rag in every room in your home, and you might consider offering one to your guests when they walk through your door, as your Bullmastiff will most certainly slobber on them as well -- Bullmastiffs do not discriminate with their slobber. Bullmastiffs are active but do not require excessive exercise, and can live happily anywhere, including apartments, as long as they have lots of company and are given lots of attention.
Bullmastiff Training :
The Bullmastiff is harder to train than most other dog breeds. He learns new commands more slowly than the majority of other breeds. You will need to be extra patient when Training him.
Bullmasiff Grooming :
The short coat of the Bullmastiff only requires an occasional brushing. But because he sheds you may find yourself brushing him once or twice a week to remove loose hair. (What you get out with a brush doesn't fall out in your home!)
source : alldogbreeds.com