The article describes the methodological differences of approaches to the concepts of: the potential of the individual, mental capacity, the adaptive capacity of the person, adaptation, adaptability. The relationship and gives us the definition of the concepts discussed. By studying the structure of the potential of the person, we show that in the majority of works are selected and described by different criteria (indicators, systems), we are considering the phenomenon of older teens to adults. Purpose - to identify various characteristics of the individual displays building or adaptability as individual mental properties of the person, which determines the boundaries of its adaptive capacity in children with mental retardation (PDD) compared with children with normal psyche development (NPD). The theory is that in the process of adaptation to new activity conditions on the stage of transition into middle (basic) school children of pre-adolescent age show adaptability peculiarities on its examined components: personally-psychic, socially-individual, subjective-pragmatical which are determined by a form of dysontogenesis. Moreover there are commonage adaptability characteristics peculiar to children with normal and delayed type of development. Children of 10-12 from the above mentioned categories studying in comprehensive schools took part the experiment. A number of psychological indicators of students with mental retardation and the NPD, which are diagnostically valuable to the success of the entry of these children into the situation of a new phase of educational activity (at the II stage of education). The analysis of the process of adaptation mechanisms in younger adolescents with mental retardation and the NPD. Obtained diagnostic indicators, methods of studying the performance and characteristics of psychological components of mental adaptability of younger teenagers with mental retardation and the NPD in the transition from primary to basic school. The authors offer a specially developed and tested psycho-diagnostic system that allowed us to study the characteristics of adaptability of students 10-12 years with PDD and the NPD. The variants of adaptability (active-adaptive, situationally-adaptive, passive-adaptive, conditionally-adaptive), shown by schoolchildren of 10-12 with a delayed and normal psychological development are distinguished and described.