The author publishes a series of statistical data on population, mainly from the Archives nationales in Paris. In the first place, he evaluates two major censuses of Napoleon's Illyria: the one which was carried out in 1809 by the French military authorities with the help of local Austrian civil servants is, generally speaking, not reliable. The other went off in 1811, together with important administrative and territorial reshaping of the Illyrian provinces. The 1811 census data for the Slovenian ethnical territory are being wholly published for the first time. Comparing the 1811 census for Carniola with the 1817 Austrian data for the same duchy, the author is able to assert the reliability of the French results, which are entirely comparable to the Austrian census. More than half of 1817 Austrian Hauptgemeinden covered the same area as the 1811 French arrondissements communaux.