The diffusion coefficient values of the Cu(II) complex compounds with EDTA, DTPA, NTA, Quadrol, glycerol, saccharose, (+)- and (+/-)-tartaric acid, OH- ions obtained by polarographic measurements in alkaline solutions lie in the range (1.2-5.7) x 10(-6) cm(2) s(-1) (at 20 degreesC and J = 3) depending on the size of complex species, and are less than those of free (hydrated) Cu(II) ions and methanediol anion (H2C(OH)O-) determined under the same conditions which are 7.0 x 10(-6) and 10 x 10(-6) cm(2) s(-1), respectively. The linear dependence of the polarographically determined diffusion coefficient values on the inverse radius of Cu(II) complex species is observed.