Calculations on the energy subband structure and the thermopower of modulated nanowires with variable cross-section are reported. It is assumed elastic scattering by point neutral scatterers. Thermopower enhancement has been previously predicted for nanowires due to 1D energy subband structure. Here, it is found an even more significant thermopower enhancement due to the energy minibands structure of the nanowires with a dot-like modulation of their cross-section. The energy dispersion spectrum of periodically modulated nanowires has been found drastically modified compared to that of straight nanowires. It is composed out of a rich structure of characteristic energy minibands. At low T, the thermopower has been found significantly enhanced and shows a dot-like behavior. The wire-like behavior is restored at higher T where the minibands structure is screened by thermal broadening. The obtained results provide insight to mechanisms present in non-uniform nanowires that have been proposed for enhancement of the thermoelectric efficiency at the nanoscale.