Job satisfaction is experience highly desirable by all people who carry out professional activities. While determining job satisfaction, we take into consideration such factors as job environment (e.g. pay, working hours, workload) and personal qualifications. This work focuses on personal qualifications. Level of the differentiation of self and job involvement were taken into account as two factors related to job satisfaction among people working in services. The research was conducted among 221 workers in service sector. There were such research tools as the Job Satisfaction Scale (SPP) by Zalewska (2003), The Differentiation of Self Inventory at Work (Cavaiola in 2012) and Ulrecht Work Engagement Scale (Schaufeli in 2002). Research findings indicate that individual interpersonal resources play a crucial role in job satisfaction. People who are satisfied with their job are more involved in it and they have a higher level of differentiation of self at work. Job satisfaction is explained by those factors of the differentiation of self which are interpersonal. The findings may serve to plan trainings for workers in service sector.