If one of your parents, grandparents, or great-grandparents were born in the region used to be Poland and fulfills the requirements of the Ancestry program then you have the right to confirm your Polish citizenship.
In order to get Polish citizenship by ancestry you don’t even need to reside in Poland and prove the knowledge of polish language, culture and history. Furthermore, you don’t have to renounce your current citizenship, as Poland accepts dual citizenship without any exceptions and restrictions.
However, you have to confirm that you were Polish all along through several generations according to all criteria of Polish law.