Tertiary substituted (fluorinated) benzenesulfonamides were synthesized in superacid HF/SbF5 and tested as inhibitors of human carbonic anhydrases (hCAs, EC 4.2.1.1). Strong selectivity toward tumor-associated hCA IX, without inhibiting the offtarget hCA II, was observed, pointing out to a new mechanism of action compared to classical sulfonamides.