The aim of the paper is the characterization of mental representations in regard to their nature, kinds and ways of existence. The paper shows different approaches to mental representations in the philosophy of mind, and especially focuses on the theories of mental content. The main part of the paper deals with the problem of epistemological commitments of cognitive representational systems in regard to the nature and kinds of mental representations which play their role in creating our knowledge and our model of the world. Here also many controversial questions is asked and discussed. In conclusion, the representational standpoint is enriched by the requirement of the representation of 'self' and the representation of body.