A process for obtaining therapeutically active 2-[4-(3- and 2-(fluorobenzyloxy)benzylamino]-propanamides and their salts with pharmaceutically acceptable acids with a high degree of purity, i.e. with a content of dibenzyl derivatives impurities lower than 0.03% by weight. The process is carried out by submitting a Schiff base intermediate to a reduction reaction with a reducing agent in an amount of organic solvent to allow the formation (and presence during a substantial portion of the reduction reaction) of a suspension of the Schiff base.