One of the main problems of most humans is professional identity. The career choice determines a person's life and potential realization. To make the right choice, one's should consider all factors that influence this process. The article presents an analysis of key factors of choosing a profession. All aspects of professional identity are divided into external and internal factors. External or objective factors do not depend on the individual, and influence from outside (social influence, job prestige, office location, salary, and others). Internal or subjective factors include professional attitude, enthusiasm for work, professional education, self-education, interest in work, professional skills. Also, the formation of the "self-identity" via which a person can use his strengths and improve his weaknesses plays the leading part. We tested the significance of external and internal factors in empirical research involving individuals aged 25 to 45. We used a semi-standardized interview with the integrated Dembo-Rubinstein method, which allowed us to build a precise dialogue plan with the respondents and deepen their answers. We formed the list of suggested factors based on a preliminary theoretical analysis of the literature presented in this article's introduction. As a result, we found the main determinants in objective and subjective factors. In general, we found that subjective factors prevail over objective in career choice. This conclusion was statistically confirmed using the Student's T-test. Therefore, it is possible to attract people to work only by satisfying their internal needs. For these reasons, they are ready to stay in their professions, despite some external inconveniences. Moreover, it is for the sake of personal needs that they are ready to look for and change their jobs, professions, and lives.