ENThe author of the article discussed creative activities of Mykolas Kado, a still not well-known architect of the end of the 18th c. - the beginning of the 19th c., in Ruzany - a township near Slonim (present Byelorussia) that belonged to the Sapiegos. Biographical data on the architect is presented and relevant literature (which is not abundant) is overviewed. The 18th c. history of construction of Ruzany palace and the design for the palace worked out by Jonas Samuelis Bekeris (not implemented) are briefly reminded. The author analyzes the still not attributed architectural drawings and designs stored in the Graphic Room of Warsaw University Library. Based on the analogues of the architectural solution, peculiarities of designs, written sources, and real life studies, he attributes to M. Kado the designs No. 813, 760, 761, 787, 795, 807, 815, 816, and 820 from volume 7 of the Sapiegos Collection. It has been also established that these drawings were intended for the reconstruction of Ruzany Palace and the construction of town buildings (hospital, trade pavilion with a tower, town hall, etc.). The design for the trade pavilions that employs simple laconic forms reflecting the influence of the rationalist French architecture is considered to be the most successful and important. The designs discussed in the article were not realized, however, their analysis helps get to know both the creative evolution of the architect and the general situation in the country. Based on M. Kado designs of Ruzany period the author asserts that the ideas of the French “revolutionary” architects of the last decade of the 18th c. were well- known in the lands of the former Lithuanian-Polish state.