[en] By potentiometric method using amalgam - cadmium dropping electrode complexing cadmium ions with N - methyl, N - ethyl -, N - isopropyl -, N - butyl -, N₁N¹-dietyl-, N₁N¹-dibuthyl-, N₁N¹-trimethyl-, N₁N¹-methylphenyl-, N₁N¹-dimethylphenylthio urea in aqueous and aqueous-ethanol solution at 25 deg C and ion force of solution equal 0,1(LiCl)₄) was studied. Composition and stability constants of cadmium complexes with above mentioned ligands were calculated. The dependence of the complex compound stability on the nature and quantity of substituent was analysed