Treatment of experimental dependence of the translational friction coefficient on molecular weight, f(M), obtained for semi-flexible macromolecules, is discussed. A draining effect is significant for these chains and must be taken into account to determine the correct values of unperturbed dimensions of the macromolecule. For this purpose a new relation between the Flory factor P and the scaling exponent b (in the equation f = K(f)M(b)) has been proposed. According to the Yamakawa theory developed for translational friction of the wormlike chains, the relation is valid for macromolecules with any length exceeding two times the statistical segment length, and with any diameter. The method has been applied to hydrodynamic properties of poly(chlorohexyl isocyanate) in carbon tetrachloride.