According to article 65 EPC any Contracting State may, if the European patent as granted, amended or limited by the European Patent Office is not drawn up in one of its official languages, prescribe that the proprietor of the patent shall supply to its central industrial property office a translation of the patent as granted, amended or limited in one of its official languages at his option or, where that State has prescribed the use of one specific official language, in that language. In accordance with this regulation each European patent covering Poland has to be validated. A translation into Polish is needed and patent holder is obligated to pay for a publication of such a document in the official patent bulletin as well. If those conditions are not fulfilled European patent will be void in Poland.
To validate an European patent due procedure is to be conducted before Patent Office of the Republic of Poland (see an example). The bill regulating validation you can find here (in Polish). Please note that every patent holder having his or her seat abroad generally has to be represented by Polish patent attorney.
If you seek an assistance in European patent matters please do not hesitate to contact me or to check up on my credentials.