Optimization of electrostatic lenses was successfully achieved by using the cubic spline method or theapriorigiven multielectrode approach. In this article we propose optimization of electrostatic deflectors by using the cubic spline method for the purpose of attaining the minimum beam spot size. We propose the reconstruction of the electrodes of electrostatic spline deflectors in terms of the optimized first harmonic field distribution functions. Our calculations show that geometrical deflection aberrations can be reduced by 2–3 orders of magnitude.