SummaryAim: The main aim was to develop a Polish version of the STQ-Now, an American questionnaire created by Stewart and colleagues to evaluate the current sibling relationship.
Method:The sample of 416 adults, 18 to 36 years old, completed a survey that consisted of a sociodemographic form, the STQ-Now and one of three questionnaires: the ASRQ, the SWS or the UCLA.
Results:The five-factor structure of the STQ-Now was validated using confirmatory factor analysis, however, because of the low level of reliability of one of the scales (Longing) some changes were introduced: items included in Longing were distributed between Mutuality and Apathy and 7 items from Criticism formed a new factor -Predominance. The new model was well-fitted to the data. The internal consistency of all scales was high (Cronbach's α 0.719 to 0.935). The Pearson correlation coefficients for STQ-Now and ASRQ, SWS and UCLA showed a satisfactory level of concurrent and discriminant validity.