<p>Results from studies of the capillary properties after thermal stabilization of bilayer knitted fabrics containing functional polyester yarns in their structures are presented. Theoretical and experimental dependences of the maximum water absorption and water-absorption coefficient on temperature and duration of thermal stabilization are obtained and allow the selection of a treatment regime as a function of the given capillary properties. Determination of the water-absorption parameter from the mass of liquid spontaneously absorbed by the material was recommended to find the functional difference of samples as a function of the surface morphology of the polyester yarn contained in the knitted fabric. A method for determining the liquid diffusion coefficient from the maximum water absorption and the thickness of the tested material was proposed.</p>