Different polymers were synthesized using ionic-imprinting technique in order to separate lanthanides by liquid-solid extraction as a model for actinides/lanthanides separation. Those materials were based on vinylpyridine, acrylic acid, or a diethylene triamine pentaacetic acid derivative. We have studied the influence of the structure of crosslinking agents and the use of monomeric complexing agent. A significant increase in the selectivity of complexation is obtained when the material is prepared in the presence of the target ion.