Aim of the study:
The main aim was the Polish adaptation of STQ-Now, an American questionnaire describing the current sibling relationship by R. Stewart and co-workers.

Subject or material and methods:
The sample of 416 adults, aged 18 – 36 years old, completed a survey that consisted of a sociodemographic form, STQ-Now and one of 3 questionnaires: ASRQ, SWS or UCLA.

Results:
Factor Analysis (CFA) confirmed five-factor structure of the STQ-Now, however because of the low level of reliability of one of the scales (Longing) some changes were made. Firstly, items included in Longing were distributed into Mutuality and Apathy. Then 7 items from Criticism formed a new factor Predominance. The new model was well-fitted to data. The internal consistency of all scales were high (Cronbach's α from 0.719 to 0.935). The Pearson correlation coefficients between STQ-now and ASRQ, SWS, and UCLA showed satisfactory level of concurrent and discriminant validity.

Discussion:
The Polish adaptation of STQ-Now consists of 48 items, examining the sibling relationship. Statistical and theoretical analyses led to the five-factor model with following scales: Mutuality, Criticism, Predominance, Apathy and Competition. Some limitations of the questionnaire were also mentioned in the article.

Conclusions:
In spite of some differences with regard to the original version, STQ-Now is a valid and reliable questionnaire and can be used in the Polish population.