Analyzing historical evolution of the two concepts, the author raises the question: why does contemporary usage of these notions often entails loss of their original sense? Reconstructing the logico-metaphorical structure of the said concepts, the researcher resorts to such methodical procedure as construction of cognitive schemes of the notions of tyranny and dictatorship. The schemes visually demonstrates similarity of the metaphorical structures of both notions differently oriented, however, in the evaluation of the situation: positively (dictatorship) and negatively (tyranny). And although these concepts are almost synonymous in contemporary scientific discourse and common vocabulary, there still remains a gap between the two connotations: the positive and the negative, and “language games” with the utilization of this gap turns into an important element of political rhetoric.