Nadja: The name is not too common, in Poland today there are only 17 with the name, in 5 provinces:
Nazwisko Ogólna liczba Rozmieszczenie
Hnatow 17 Gd:13, Pt:1, Pł:1, Rz:1, Ta:1
These figures are from Dr. Rymut's 1990 Survey of Polish names, which is linked from Polish Roots.
http://www.herby.com.pl/There is a table of the province abbreviations.
My paternal GrGrandmother Maria was a Hnatow. She is buried in Walawa, Podkarpackie province.