In the last few years the physical properties of semiconductor nanostructures have been intensively investigated [1-3]. Spatial confinement of phonons or charge carriers in nanostructures leads to the quantification of their energy spectra. In this work we report on the theoretically investigation of electron energy spectra in cross-section-modulated silicon nanowires (NW) with dielectric coatings. The influence of the geometric parameters of the NW on its electron spectra has been analyzed. The schematic view of a cross-section-modulated NW is presented in Figure 1. Figure 1. Schematic of the cross-section-modulates NW showing notations for NW sizes. Employing the effective mass approach we have calculated quantized electron energy spectra, using one band Hamiltonian [2] with taking into account an effective mass anisotropy in Si, and difference between effective masses in silicon and silicon dioxide. Figure 2 shows the electron dispersion in different NWs (NWs dimensions are indicated in figure caption). From Fig. 2 one can conclude that nanowire claddings weakly influence the electron energies (see Figs. 2(a,b)), while rise of Lx,1 leads to the increasing of dispersion curves slope (see Fig. 2(a,c)). The latter is explained by the attenuation of an electron confinement in narrow nanowire segments with Lx,1 augmentation. Our results shows that change of geometrical parameters of the NW can significantly influence their electron properties.