Abstract The hydrodynamic and dynamo-optical properties of carboxymethylcellulose with M = (39 − 370) × 10 3 and degree of substitution 0·9 ± 0·1 in cadoxene and cadoxene plus H 2O (1:1) have been investigated. Equations are obtained relating the characteristic viscosity and the sedimentation and diffusion coefficients to the molecular mass. Enlisting the theories of the hydrodynamic properties of worm-like chains for carboxymethylcellulose in cadoxene the authors calculate the length of the Kuhn segment A = 130 ± 20 A ̊ which proved to be close to the A value for cellulose. For solutions in cadoxene with water the magnitude A is 1·5−2 times higher. The optical shear coefficient and the optical anisotropy of the statistical segment of carboxymethylcellulose are close to the corresponding values for the cellulose chain in the same solvent.