Objectives. Amid increasing adolescents’ immersion in media information and their vulnerability to mis/disinformation and the screen time negative health correlates, competences of critical thinking about health gains in significance. The Claim Evaluation Tools (CET) assess the understanding of claims about treatment effects and enable critical health literacy measurement in different populations. It has not been adapted and tested in Central Europe before. Design, The process of cultural adaptation covered three phases: translation and cultural adaptation, testing and psychometric analysis. We used Classical Test Theory and Rasch analysis to verify the validity and reliability of the Polish version of the CET. Additionally, we tested known-group and convergent validity. Setting. The pilot test was conducted on a pupils sample from eight purposefully selected schools in Southern Poland, and the final version of the tool has been tested on a national study sample of pupils of primary schools randomly selected from all Polish regions. Participants. We collected the data from a national sample of 2242 pupils aged 12 to 15 years, attending sixth to eighth grades, from 42 primary schools. Results. We applied some changes to the multiple-choice questions (MCQ) scenarios and wording of some of the options based on the expert’s opinions. We validated 24 MCQs reflecting 12 claims about treatment effects (2 MCQs per claim). The psychometric properties of the Polish version of the tool are satisfying. Conclusions. The Polish version of the CET can be applied to measure critical health literacy among 12- to 15-year-old adolescents as well as to evaluate educational interventions promoting the understanding of healthcare claims in Poland.