[en] The role of the growth conditions onto the spin transport properties of silver (Ag) have been studied by using lateral spin valve structures. By changing the deposition conditions of Ag from polycrystalline to epitaxial growth, we have observed a considerable enhancement of the spin diffusion length, from ${\mathrm{\lambda <!--\; ??\; -->}}_{\text{Ag}}=449\pm <!--\; ??\; -->30$ to $823\pm <!--\; ??\; -->59$ nm. This enhancement in the spin diffusion length is closely related to the grain size of the Ag channel, which is 19   ±   6 nm for polycrystalline Ag and 41   ±   4 nm for epitaxial Ag. This study shows that diminishing the grain boundary contribution to the spin relaxation mechanism is an effective way to improve the spin diffusion length in metallic nanostructures. (paper)