We have to distinguish biological and representation-dependent selves while dealing with human beings. The biological self is the human being as an animal with skin which marks a biological border to the environment. The representation-dependent self is nothing but a human being with special forms of information processing including self-representations. The boundaries of the self are essentially dependent on the kind of representation that is available for a subject: After critizing different models of self-consciousness as proposed by Neisser and Bermúdez, a new positive account inspired by developmental psychology will be presented which systematically distinguishes five different levels of self-consciousness, that comprise nonconceptual representations of bodily states, conceptual representation of objects, sentential representation of events, meta-representation of propositional attitudes (like beliefs, desires etc.), and, as the most complex form, iterative meta-representations of propositional attitudes. Then the central claim is developed that the boundaries of the self are essentially dependent on the kind of representation that constitutes the self. This allows us to account for phenomena like alien limb syndrome as well as for thought insertion.