A new series of tetrazole-, oxadiazole-and cyanosubstituted 1,4-dihydropyrimidinone compounds were synthesized, and their inhibitory effects on the activity of purified human carbonic anhydrase (hCA) I were evaluated. 4-Cyanophenyl-1,4- dihydropyrimidinone compounds were prepared with 1,3-diketone, cyanobenzaldehyde and urea. The compounds were reacted with sodium azide and then with anhydride to get the final products. The results showed that all the synthesized compounds inhibited the CA isoenzyme activity. The compound 4-(1,7,7-trimethyl-2,5-dioxo-1,2,3,4,5,6,7,8-octahydroquinazoline- 4-yl) benzonitrile 6c (IC50 = 0.0547 mM) has the most inhibitory effect.