Imposition of Ashes - where in Catholicism is it commonly practiced?

Since I learned of this practice, I thought that placing ashes on Ash Wednesday is practiced worldwide, at least within the Roman Catholic Church. But now I have been to a Mass (on the first Lent Sunday, when ashes may be placed for those who didn't receive this sacramental on Ash Wednesday) attended by some Portuguese people. They seemed puzzled when they saw the priest placing ashes on other worshipers - they apparently didn't know the practice. I checked the Czech (I'm Czech) and English Wikipedias, and they both highlight the practice of placing ashes. I don't speak Portuguese, but Portuguese Wikipedia has no ashes-themed picture and from the little I understand, it seems that this practice is not even mentioned there. Anyway, Portugal is unlikely to be the only country not observing imposition of ashes. English Wikipedia gives a list of churches observing Ash Wednesday, but not one of countries where the practice of placing ashes is (or is not) observed in the Roman Catholic Church. Is there any such list?