A series of fluorinated polyurethanes, characterized by a segmented structure containing hard segments based on 4,4 ' -methylenebis(phenylisocyanate) (MDI) and 1,4-butandiol (BDO), were analyzed by small- and wide-angle X-ray scattering and transmission electron microscopy (TEM) in order to study the influence of the synthesis and of the soft and hard segments length on the structure. Theoretical models of lamellar morphology were used to fit calculated small-angle scattering patterns to the experimental ones. TEM and small-angle X-ray scattering analysis shows that these polymers are characterized by a heterogeneous structure, not only at the molecular level, but also at a macroscopic scale.