ENThe text is the first of two parts of the study on the construction works on the property of one of the most important Lithuanian magnates of the first half of the 17th century, Krzysztof Radziwiłł (1585–1640), the Vilnius voivode and the Grand Hetman of Lithuania. It discusses the figure of the investor, attempts to assess the scope of construction works on his private estates and, to a lesser extent, also on royal estates managed by him. Three different periods of Radziwiłł’s construction activity were distinguished. Changes in the intensity of work were caused to a greater extent by the intentional decisions of the investor than by financial or other factors. The author also tried to present the changing financial possibilities of the magnate, which peaked in the last years of his life. The process of investment planning is also presented, which often changes over time. Attention was drawn to the very important role played in this respect by the investor who decided about each stage of the investment. Although he consulted his decisions with his trusted entourage, primarily with property managers, he left the final decision for himself. This had consequences in the form of farreaching incapacitation of state officials and often unnecessary prolongation of investments. The latter was caused by a significant dispersion of land estates and communication difficulties. Keywords: Krzysztof Radziwill; Voivode of Vilnius; Great Hetman of Lithuania; Grand Duchy of Lithuania; magnate estate; residences; construction; financing of construction works. [From the publication]