In the present paper an estimation was given of total specific area (S) of very clayey soils of smonitza type in Central Serbia on the basis of the data on their textural composition and maximal hygroscopic moisture. Total specific area (m²g^-1) of the analysed very clayey smonitzas is, on average equal to the product of maximal hygroscopic moisture (MH), expressed in percent ratio of the mass, and the coefficient 11.50, i.e. S = 11.50*MH (m²g^-1).