The targeted delivery of radionuclides to tumours holds great promise for diagnosis and treatment of malignant neoplasms. The development of scaffold proteins has significantly simplified the design of targeting agents with desirable properties. This review comprehensively describes the key aspects of the design of radionuclide compounds, including classification of radionuclides, methodology for their attachment to targeting agents and characteristics of these agents that affect their behaviour in the body. Various targeting molecules are compared in terms of their ability to specifically find malignant foci in the body. The most recent achievements of cancer theranostics that aim at increasing the selectivity of antitumour effect are described, such as the fusion of targeting scaffold proteins with the albumin-binding domain and pretargeting. Special attention is paid to the creation of targeted radionanomaterials. Advantages and disadvantages of different strategies are analyzed and approaches for improving the delivery to tumours and for minimizing the undesirable impact on healthy organs and tissues are proposed. Particular emphasis is placed on the results of studies published in 2020 ?? 2021 that have not yet been covered by reviews.