The half-wave resonance of ultra-thin conductors produced by different technologies is investigated within 8.2–15.5 GHz frequency range using an open quasi-optical resonator. A comparison of the theoretical and experimental results show that for glass-coated and drawn microwires, both fabricated from alloys with specific conductivity of over 105 S/m, the experimental value of the microwire resonant length is less than the theoretical. Supposedly, this is due to the surface effect including the nanoscale transition layer of microwires. Dependence diagrams are obtained for microwires made of alloys with natural ferromagnetic resonance. It is shown that the half-wave length resonance of the latter is considerably longer than that of microwires with a similar value of specific conductivity, but without magnetic properties.