FIELD: organic chemistry, heterocyclic compounds, biochemistry. SUBSTANCE: products: derivatives of pyrazolo-[4,3-d]-pyrimidine-7-one's of the general formula (I) R1 where (C1-C3) - R2-alkyl group; R3 and (C1-C6) - R4-alkyl group; (C1-C4) - (C1-C4)-alkyl group optionally monosubstituted with hydroxy, carboxy, N,N-di-NR5R6-alkylcarbamoyl group or group (C2-C4), (C1-C4)-alkenyl group optionally substituted with cyano, N,N-di-CO2R7-alkylcarbamoyl group or group (C2-C4), NR5R6-alkanoyl group optionally substituted with group (C2-C4), hydroxy-NR5R6-alkyl group substituted with group (C2-C3), (C1-C2)-alkoxy-(C1-C3)-alkyl group optionally substituted with hydroxy or morpholino-group, halogen atom, carboxy-group, 4-SO2R8-alkylpiperazinocarbonyl group, pyridyl or imidazole group optionally substituted with methyl group, or group NH-R5; R6 and (C1-C4) are independently hydrogen atom or R9-alkyl group, or taken together with nitrogen atom to which they are bound form morpholino- or piperidino-group optionally substituted with methyl or hydroxyl group, or 4-R7-1-piperazinyl group, or imidazolyl group optionally substituted with methyl group; (C1-C4) - hydrogen atom or R8-alkyl group; (C1-C3) - R10-alkyl group optionally substituted with morpholino-group or 4-R9-1-piperazinyl group; (C1-C3) - hydrogen, R10-alkyl, 2-hydroxyethylacetyl; (C1-C3) - R1-alkyl group optionally substituted with phenyl group at condition that when (C1-C3) means R2-alkyl group, R3 - methyl and (C1-C6) - R4-alkyl group then (C1-C4) is distinct from 
-alkyl or halogen atom, or their pharmaceutically acceptable salts. Compounds of the formula (I) 
are selective inhibitors of cyclic guanosine-3', 5'-monophosphate phosphodiesterase used for treatment of cardiovascular diseases (stenocardia, hypertension, cardiac failure and atherosclerosis). Invention relates to pharmaceutical composition showing activity with respect to cGMP-phosphodiesterase. It has compounds of the formula (I) at amount 1-400 mg in mixture with pharmaceutically acceptable carrier of vehicle. Invention relates to also a method of inhibition of cGMP-phosphodiesterase activity by the indicated compounds. EFFECT: improved method of synthesis, enhanced effectiveness of compounds. 7 cl, 3 tbl
