A series of aromatic/heterocyclic sulfonamides incorporating phenyl(alkyl), halogenosubstituted-phenyl- or 1,3,4-thiadiazole-sulfonamide moieties and thienylacetamido; phenacetamido and pyridinylacetamido tails were prepared and assayed as inhibitors of four physiologically relevant carbonic anhydrase (CA, EC 4.2.1.1) isoforms, the cytosolic human (h) hCA I and hCA II, and the mitochondrial hCA VA and hCA VB. The new compounds showed moderate inhibition of the two cytosolic isoforms (K(I)s of 50-390nM) and excellent inhibitory activity against the two mitochondrial enzymes, with many low nanomolar inhibitors detected (K(I)s in the range of 5.9-10.2nM). All substitution patterns explored here lead to effective hCA VA/VB inhibitors. Some hCA VA/VB selective inhibitors were also detected, with selectivity ratios for inhibiting the mitochondrial over the cytosolic isozymes of around 55.5-56.9. As hCA VA/VB are involved in several biosynthetic processes catalyzed by pyruvate carboxylase, acetyl CoA carboxylase, and carbamoyl phosphate synthetases I and II, providing the bicarbonate substrate to these carboxylating enzymes involved in fatty acid biosynthesis, their selective inhibition may lead to the development of antiobesity agents possessing a new mechanism of action.