Cascade polymer complexes containing a) complexing ligands of general formula I A—{X—[Y—(Z—( W—Kw)z)y]x}a  (I)  in which A stands for a nitrogen-containing cascade nucleus of base multiplicity a, X and Y, independently of one another, stand for a direct bond or a cascade reproduction unit of reproduction multiplicity x or y, Z and W, independently of one another, stand for a cascade reproduction unit of reproduction multiplicity z or w, K stands for the radical of a complexing agent, a stands for numbers 2 to 12, x, y, z and w, independently of one another, stand for numbers 1 to 4, provided that at least two reproduction units are different and that 16≦a·x·y·z·w≦64 holds true for the product of the multiplicities, b) at least 16 ions of an element of atomic numbers 20 to 29, 39, 42, 44 or 57-83 and c) optionally cations of inorganic and/or organic bases, amino acids or amino acid amides are valuable compounds for diagnosis and therapy.