This paper explains how parasitic resistances of the choke and capacitor affect the operation of a DC-to-DC boost converter. The second chapter explains the basic principle of operation of a DC-to-DC boost converter without parasitic resistances, and describes the operating modes in which the converter can operate (continuous and discontinuous operation). The third chapter theoretically explains the influence of parasitic resistances on the operation of the converter, as well as the principle of experimentally determining the actual parasitic resistances of the capacitor and choke. Then, the fourth chapter discusses the method of applying a simulation model for the purpose of determining the influence of parasitic resistances of the choke and capacitor. In the fifth chapter, we have tried to clearly demonstrate the influence of parasitic resistances on the operation of the converter, using comments and images of the voltage and current waveforms of individual converter components, for three cases. In the first case, we explained how the converter would operate without parasitic resistances. In the second, we included the parasitic resistance of the choke and tried to compare it with the first case. In the third case, we took into account the parasitic resistances of the choke and capacitor and explained how these two components combined affect the operation of the converter.