In the master’s thesis we were interested to explore if differentiation of self and adult attachment are important predictors of relationship satisfaction, what is the degree of satisfaction in relationship considering attachment style and what kind of differentiation of self is considering attachment styles. Our sample included 240 participants (53,8 % of women) who have completed the Relationship Questionnaire - RQ, Differentiation of Self Inventory – DSI and Relationship Assessment Scale - RAS. We have confirmed that people with avoidant attachment more frequently use emotional cutoff, meanwhile people with preoccupied attachment more frequently use emotional reactivity and fusion with others. There was no significant difference between men and women in relationship considering attachment styles, because women and man are approximately equally satisfied and there was no significant difference in length of relationship considering attachment style. This study offers a new perspective and understanding correlations of these constructs, also leaving open space for further research and better understanding of even the most complex area such as partnership.