The article summarizes the results of the theoretical study of the problem of diagnostics designing that takes into account the multidimensional nature of competence. Competences aggregate inconsistent components. Therefore, in order to describe them, it is natural to apply the category of multidimensionality. The essence of the multidimensionality concept is explained in the context of the competence-centered education. Multidimensionality is the most adequate and volumetric characteristic of the described reality. Education is understood as a process of competences formation. Pedagogical diagnostics is an integral part of the learning process. The multidimensional nature of competences necessitates the development of appropriate methods and means for their diagnostics. The article clarifies the role of diagnostics as the means of education activity management. The content of the diagnostic activity is disclosed according to its three interrelated directions: control, correction, and forecasting. The following principles of pedagogical diagnostics are defined: multidimensionality, continuity, anthropocentrism, and objectivity. The diagnostic functions are specified for each of its directions. The construction of the diagnostic instruments is based on the theoretical model of diagnostics. The choice of the multidimensional vectors is substantiated for building a model of pedagogical diagnostics. The competence elements' formalization is carried out in the form of component parts of the multidimensional vectors. It is shown that the use of operations on vectors allows reflecting the dynamics of the formation of competences. The individual educational path designing is implemented by means of the vector model. DOI: 10.5901/mjss.2015.v6n4s4p11