Background. The subject matter of developmental psychology has almost never been subject to critical analysis, but it is obvious there are problems in this field. In particular, it is hard to shape the major issue of analysis in developmental psychology: personality development, psyche, age characteristics, or all of the above mentioned issues. For the further research of developmental psychology as a science, it is very important to identify the main fundamentally different areas and subject matter of research that are somehow studied, however spasmodically, often within other branches of psychology or even in other sciences.

The Objective of this paper is to clarify the subject matter of developmental psychology as a science, to verify that developmental psychology dwells on several fundamentally different areas and subject matters of research, in accordance with which it is necessary to shape the research of this science.

Design. The paper identifies fundamentally different areas of developmental psychology considered as separate subject matters of research. It is recognized that the structure of modern developmental psychology does not correspond to the subject matter of research. As a result, some areas of personality development are not identified as separate subdisciplines or sections of developmental psychology (e.g. variational personality development, development of personality substructures) lack research and are not presented in textbooks developmental psychology.

Conclusion. Developmental psychology can identify the following types of research subject matters: normative and variational human development, the development of psychological substructures of personality and psychological characteristics of age groups. It is necessary to restructure the developmental psychology based on the subjects of research highlighting the following subdisciplines: regular mental development, variable personality development, mental development (development of psychological substructures of personality), age-based studies (age groups psychology).