Article 85 of the Constitution statutes two duties of the Polish citizen. The first one is the duty to defend the Homeland and the second is the duty of military service. The same article also statutes that any citizen whose religious convictions or moral principles do not allow him to perform military service may be obliged to perform substitute service in accordance with principles specified by the statute. In this paper, the author presents the evolution of citizens’ duties in the field of defence and the evolution of the institution of substitute service, in the Polish constitutional tradition. The author also analyse the work of the Constitutional Commission of the National Assembly on the content of article 85 of the Constitution. The author compares the results arising from mentioned considerations with the actual functioning of the substitutive service in Poland since 1989. Eventually, the author presents postulate de lege ferenda of changes in the current regulation of the institution of substitute service to bring it into accordance with the historical and systemic interpretation of the Constitution.