Aim of the study:
The aim of the study was to identify personality predictors of the quality of interpersonal sibling relationships in early adulthood.

Subject or material and methods:
The participants of the study were 160 young adults (M=25.5 years; SD=3.27), coming from the district of Łódź. The applied research tools included: Adult Sibling Relationship Questionnaire – short form, Personality Inventory NEO-FFI, Emotional Intelligence Questionnaire INTE.

Results:
The obtained results indicate the occurrence of personality determinants of the quality of interpersonal sibling relationships in early adulthood. It was found out that Extraversion and Openness (only in the group of men) were determined the sibling relationships based on Warmth. Conflictual relationships with adult siblings in both groups were determined by a low level of Agreeableness, and, only in the group of women, by a high level of Neuroticism and Extraversion. Rivalry in relationships with siblings in the group of women was determined by a low level of Agreeableness. In the conducted research, emotional intelligence did not determine the quality of relationships with adult siblings. It was found out that women had obtained higher mean scores than men in respect of Neuroticism, Agreeableness and Emotional Support.

Discussion:
The results of this study are partly consistent with the results of previous studies in this area.

Conclusions:
The fact of showing the role of personality dimensions and emotional intelligence in shaping the quality of interpersonal sibling relationships in early adulthood will contribute to updating the psychological knowledge in this field and may be important for the psychotherapeutic practice.