No, we don't use the diminutive. The normal is pan/pani if you speak to the dog. If you speak to people (especially if you speak to the owner) the most used word is właściciel/właścicielka; pan/pani sounds bookish. I think that if I asked somebody "czy jest pan panem tego psa" the owner would burst in laughter or think that I am a foreigner.Hello, what do you call a master or mistress in Polish, it is a dog's (maybe other animal's) owner. May guess is: pan, pani. Czechs use the same words but with diminutives (páníček - panička), so maybe you use a diminutive, too. Thanks. E.