A new theoretical description of the interior mobility of carbosilane dendrimers has been tested. Experiments were conducted using measurements of the 1H NMR spin-lattice relaxation time, T1H, of two-, three- and four-generation carbosilane dendrimers with three different types of terminal groups in dilute chloroform solutions. Temperature dependences of the NMR relaxation rate, 1/T1H, were obtained for the internal CH2 – groups of the dendrimers in the range of 1/T1H maximum, allowing us to directly evaluate the average time of the internal spectrum for each dendrimer. It was found that the temperature of 1/T1H maximum is practically independent of the number of generations, G; therefore, the theoretical prediction was confirmed experimentally. In addition, the average time of the internal spectrum of carbosilane dendrimers was found to be near 0.2 ns at room temperature, and this value correlates well with the values previously obtained for other dendrimer structures using other experimental techniques.