A process for the preparation of solifenacin and/or the pharmaceutically acceptable salts thereof of high pharmaceutical purity is characterized in that 3-(R)-quinuclidinoloxy anion generated in situ from 3-(R)-quinuclidinol in a presence of strong base in polar organic solvent is subject to acylation with (S)-1-phenyl-1,2,3,4-tetrahydroisoquinolinecarbonyl chloride of chemical purity at least 98%, while maintaining constant anion excess in a reaction mixture, and after reaction completion solifenacin base is optionally transformed into solifenacin salt according to standard procedures. (S)-1-Phenyl-1,2,3,4-tetrahydroisoquinolinecarbonyl chloride of chemical purity at least 98% is obtained in a reaction of (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline and molar excess of phosgene in a presence of tertiary aromatic amine in aromatic hydrocarbon, and isolated in a crystalline form.