Design of complex inorganic compounds of rare earth transition 3d-metals and their template-directed synthesis is a line of research intensively pursued in the present-day inorganic chemistry, which is due to both the fundamental significance of the problem and the necessity of designing new magnetic materials for different applications [1–3]. The purpose of this study is to identify the composition – structure – magnetic susceptibility relationship in the family of compounds of the Dy–In–O system. These compounds are formed by dissolving the salts In(NO3)3 and Dy(NO3)3 in distilled water, followed by a chemical co-precipitation of dysprosium and indium hydroxides from the resulting solution using an aqueous solution of 25% ammonia рН 10 with a subsequent washing and heat treatment in air at 1000°С for 1 h. The content of indium in the solution of salts was varied from 0 to 100 at.%. An X-ray diffraction analysis was performed in a Rigaku Miniflex 600 diffractometer using CuKα-emission in the angular range 10–90° (2θ) with a scanning step of 0.02° and a recording rate of 2 deg/min. The diffraction peaks were identified using the data bases PDF 4+ and a software package for powder X-ray diffraction analysis POWDER CELL 2.4. The magnetic susceptibility was determined from the variations in the coil inductance after a powder sample had been placed into it, using an LCR Agilent E4980A precision meter, at room temperature. The measurement error was ± 3%. Figure 1 presents the dependence of specific magnetic susceptibility χ of the resulting samples of the Dy–In–O system on the content of indium. Such materials, having paramagnetic (Dy3+) and diamagnetic (In3+) ions in their compositions, demonstrate a transition from positive (164.5∙10–6 cm3/g for Dy2O3) values of χ to its negative values (–2.1∙10–6 cm3/g for In2O3). A nonmonotonic character of the dependence is likely to be due to the formation of a DyInO3 compound in the Dy–In–O system, which has a hexagonal orthorhombic structure. It follows from Table 1, presenting the XRD data for the Dy–In–O system, that the content of DyInO3 in the region of indium concentration 50 at.% reaches nearly 100%, and there is a step in the curve of specific magnetic susceptibility at the value of χ = 68.4∙10–6 cm3/g. According to the results published in [4], this compound is a paramagnet, whose magnetic susceptibility closely follows the Curie–Weiss law up to the liquid nitrogen temperature. The Curie paramagnetic temperature for DyInO3 was determined to be equal to – 258.15°С. The variations in the concentration of DyInO3 with the content of indium in the Dy–In–O system, according to the data in Table 1, correlates with the appearing kinks in the curve presented in Fig. 1. The results used in this work have been obtained within the frame of the Program for improving TSU competitiveness among the world leading research and education centers.