The authors argue that optimization of monitoring systems is a complicated task, as multiple factors need to be taken account of at one and the same time. The authors consider a monitoring system as a system of "supervision" that incorporates a set of tools, as well as registration, archiving, classification, and analysis of inspection results, inclusive of their comparison with the projected data, development and implementation of engineering solutions. The basic goal of any geomechanical monitoring project consists in development of a methodology of rational arrangement of items of monitoring equipment that employ GIS technologies. The objective of this research is to apply advanced numerical methods in combination with geographic information systems with a view to the optimization of a system of monitoring applicable to subterranean structures. Should the proven methodological and scientific validity of the research findings be in place, long-term geomechanical projections of the structural behaviour will be feasible. The proposed methodology may be introduced as a standard method of structural behaviour monitoring in the course of construction and operation of structures for engineering solutions to be made in the real-time mode. The principal goal of a monitoring system is the identification of the rock nature, processes initiated in the medium, their development pattern, and the identification of technical and economic factors of impact onto the engineering solutions to be made at each stage of engineering surveys, design, construction and operation of major subterranean structures. The analysis of calculations made for various loading scenarios have proven that any further research should take account of a lateral load that is equal to doubled vertical loads. The research was performed at a subterranean structure composed of two parallel chamber pits. The analysis of GIS modeling methods has proven that development of GIS projects requires the employment of statistical methods of the multidimensional analysis. Employment of multidimensional analysis methods makes it possible to examine the geological features that demonstrate a high degree of complexity. Terrain modeling requires the employment of models of formal characterization and differentiation. Identification of positions of geological strata and tectonic dislocations may be reduced to interpolation and extrapolation. The model of a subterranean structure is implemented in the GIS and databases, and it incorporates the data banks entitled "Rock", "Massif", "Structure and Massif", as well as the data banks. that contain surveying, geological and supplementary information. The GIS also comprises a topographic site plan, a geologic description of a massif (stratifi cation, lamination, as well as a complete assessment of each major massif crack). The subterranean structure of a radioactive waste storage site was the subject of a 3D numerical experiment. Its results were entered into the GIS project database. Positions and lengths of extensometers were optimized on the basis of the simulation performed in furtherance of the methodology developed by the authors. Positions of extensometers were registered in the GIS as reference points.