In this work, the effects of the ohmic losses on the radiation properties are extensively evaluated for the general class of the traveling-wave antennas. For arbitrary aperture distributions, rigorous analytical approaches have been developed to take into account the dissipation in conductors and/or dielectrics that can adversely affect the basic design parameters, such as efficiency and leakage constant. Consequently, fundamental information is achieved both to quantify the alterations in the antenna performances due to misappreciation of the ohmic losses and, above all, to appropriately correct the synthesis procedures for improved radiation patterns. Important applications of this analysis refer to topologies of leaky-wave antennas.