A QSAR study of two sets of carbonic anhydrase inhibitors is presented using a variety of molecular descriptors including topological indices. The first set consists of 29 benzenesulphonamides, and the second set includes 35 sulphanilamide Schiff bases. Two regression methodologies have been used involving ridge regression and the CODESSA program, and their results are compared with those of previous QSAR studies. Good correlations were found for the former set, and less satisfactory results for the latter set when the number of molecular descriptors is kept below five.