The investigation of diphosphonic acids, their derivatives, salts and coordination compounds being part of them is of scientific and practical importance. In terms of science, they are polyatomic acids, polydentate ligand systems, which determine the possibility of synthesis of mono-, bi-, polynuclear, mixed-ligand and heterometallic complexes. In terms of practice, their salts are already used now in medicine. The aim of the research carried out was to synthesize novel Pd diphosphonates and to establish the forms of their existence and structure peculiarities in aqueous solutions and crystals. For these Pd diphosphonates, anticancer activity at the cisplatin level has been established; their LD50 is higher by an order of magnitude than that of cisplatin, the chief thing being that they accumulate selectively in bone tissue. Eleven novel Pd(II) diphosphonates of mono- and bisligand composition have been synthesized and investigated. On the basis of data of potentiometric titration, electron and NMR spectroscopy and computing methods, the square-planar structure of the coordination units of compounds with bidentate coordination of ligands by the oxygen atoms of two phosphonic groups or by the oxygen and nitrogen atoms of amine group in α-position in the case of acid amino derivatives has been established. The complex species exist in solutions in different degree of deprotonation, depending on medium pH, in the case of the same composition of the coordination unit. Using computing methods and NMR 31 P data, we showed the possibility of existence of different conformations in solutions, which is due to spin-spin interaction of P nuclei, the presence of intramolecular hydrogen bonds and different mutual spatial orientation of methylene groups. A similar structure (the shape and composition of the coordination unit) and ligand coordination mode have been established by X-ray structural analysis for crystalline samples too. In the case of bisligand complexes of Pd with aminophosphonic acids, compounds of cisand trans-structure have been isolated and characterized. In mononuclear Pd(II) diphosphonates, not all oxygen atoms of phosphonic groups are involved in the interaction with the central atom; therefore, polynuclear coordination compounds: trinuclear Pd-containing, trinuclear Pd-Cu-, Pd-Ni-containing, binuclear Pd-Cocontaining compounds, in which diphosphonic acids act as a bridge, have been synthesized on their basis and structurally characterized. Pd coordination unit of square-planar structure with the same atomic environment is common to them. At the same time, a mixed-ligand environment of different type and pseudooctahedral structure of the coordination units of both atoms (Cu and Ni), which form part of compounds, which perform different functions, has been established. In all cases, the presence of numerous hydrogen bonds in crystals has been detected, which is typical of supramolecular systems.