In this paper, we investigate the space-wave leaky modes of coplanar waveguides (CPW) on cylindrical substrates and analyze their propagation characteristics. The first higher order leaky mode is assumed and propagation constants of it are solved by the spectral-domain approach (SDA). The effects of outer radii, center strip widths, and slot widths, are discussed. From our numerical results, center strip widths and slot widths play similar roles in design of these structures. Besides, we find that coplanar waveguides on cylindrical substrates have the capability to be wideband antennas.