The molecular structure of helical supramolecular dendrimers generated from self-assembling dendrons and dendrimers and from self-organizable dendronized polymers was elucidated for the first time by the simulation of the X-ray diffraction patterns of their oriented fibers. These simulations were based on helical diffraction theory applied to simplified atomic helical models, followed by Cerius2 calculations based on their complete molecular helical structures. Hundreds of samples were screened until a library containing 14 supramolecular dendrimers and dendronized polymers provided a sufficient number of helical features in the X-ray diffraction pattern of their oriented fibers. This combination of techniques provided examples of single-9(2) and -11(3) helices, triple-6(1), -8(1), -9(1), and -12(1) helices, and an octa-32(1) helix that were assembled from crownlike dendrimers, hollow and nonhollow supramolecular crownlike dendrimers, hollow and nonhollow supramolecular disklike dendrimers, and hollow and nonhollow supramolecular and macromolecular helicene-like architectures. The method elaborated here for the determination of the molecular helix structure was transplanted from the field of structural biology and will be applicable to other classes of synthetic helical assemblies. The determination of the molecular structure of helical supramolecular assemblies is expected to provide an additional level of precision in the design of helical functional assemblies resembling those from biological systems.