Nowadays the number of traditional boundary marks that shall clearly tell if the person already reached adulthood or not is being reduced. Thus this is not absolutely evident who is in present-day society considered as adult person. Which characteristics and signs shall have such adult person? What does it mean actually the conception of adulthood latterly? In this thesis I have focused on social representation of the adulthood concept and adult person, namely in the group of young people of age between 18 and 25 years that are situated in the period of life Emerging Adulthood as it is envisaged by J.J. Arnett. The research combines qualitative and quantitative approach on its basis is possible to obtain more complex information about the problems. Research set consists of 160 respondents that were split on students, employed students and employed persons (not student). Based on their responses on the questionnaire containing opened questions in term of qualitative part I have set together base categorical and sub-categorical systems of social representations related to the concept of the adulthood and those what the adult person can and needn’t, know and doesn’t know, should and should not. In terms of quantitative part of the thesis I was investigating whether among mentioned categories exist mutual statistically significant relations and further more also whether statistically significant relations exist between presented category and status of the respondent as student, employed student and employed person (not student). Results of this thesis contain descriptions of discovered social representations and mutual significant relations.