The aim of this paper is to analyze the provisions of the “draft Constitution of the Polish State” of July 1917 – an original achevement of the Polish doctrine of state law. In the opinion of the majority of contemporary representatives of Polish constitutional law, the activities of the Provisional Council of State of the Kingdom of Poland, as well as the Regency Council – bodies composed of Poles, but appointed by the German occupation authorities in 1916–1917, were meaningless, and the bodies themselves were imposed from outside and pursuing foreign interests. As a consequence, the value of the systemic achievements of these bodies and its meaning is denied. However, the analyzed document developed under the auspices of the Provisional Council of State of the Kingdom of Poland was chronologically the first full draft constitution for Poland after the state regained its independence. It is an interesting and original testimony to the high substantive level of Polish science of constitutional law developing in the absence of Polish statehood. It is also a proof that a mixed (constitutional) monarchy was considered to be the optimal political system for rebuilding statehood after more than 120 years of non-existence. The fact of fully Polish authorship of the project (mainly in the persons of prominent professors of law) may be a counter-argument against the thesis that the idea of a monarchical system for the Polish state reactivated in 1918 was completely foreign and imposed from the outside. Although the Polish political elites in 1918 ultimately gave up the idea of introduction of a constitutional monarchy in Poland, some of the solutions contained in the 1917 draft constitution became an inspiration for later systemic projects, both submitted during the work on the first full constitution of an independent Polish state enacted in 1921 as well as during the subsequent discussions on its revision.