Lillasophe - you are doing the correct thing, asking lots of questions, prior to purchasing a pup. It is very difficult for any one to give you the answers you desire. Sometimes it is easier to know, what you must AVOID. As explained by Igmusta - showlines of any kind - as clearly these are breed with appearance in mind. Even if the breeder claims the breed is a natural guardian and when you need it it will guard. The fact is the pups are products of their genes and will have those traits their parentage had. That said you may still get pups unsuitable as guards even with the best parents! If I use an example of some dogs I have known - one of the best guard dogs was a Bullmastiff - great with kids and obedient etc but a REAL guardian. This dog was like the real old type Bullmastiff as this breed was originally bred to be able to effectively deal with a real - life or death situation and protect it's owner at all costs. However it would probably finish last in a Bullmastiff dog show. And so was never used at stud and therefore these outstanding genes have not been passed on. I have also known some Bullmastiffs who are hopeless guards or even watchdogs. Several which have done nothing when real life situatons have presented themselves and the dogs have failed miserably - But they were great at dog shows and therfore were used as Stud dogs repeatedly! So more often than not these are the foundations for this breed in the UK. That is the problem with generalisations I suppose. Every breeder has a different notion of what is important and how they prioritise these qualities. So it is not so much the BREED but the Lines within the breed.