[en] We report a temperature and frequency dependent electron spin resonance (ESR) study of the kagome spin-1/2 compound ZnCu₃(OH)₆Cl₂. Our results demonstrate that two spin species are simultaneously detected; copper spins on the intra-plane Cu²⁺ kagome sites and those on the inter-plane Zn²⁺ sites, the latter resulting from the Cu²⁺/Zn²⁺ antisite disorder. We examine all the possible magnetic anisotropy terms, which could lead to the observed extremely broad ESR lines in this system. We argue that the line broadening is due to Dzyaloshinsky-Moriya interaction.