Introduction: Instruments of quality of life related to oral health are used with increasing frequency in research. However, these instruments are not available in all countries or languages. The availability of multilingual versions of instruments, valid for different cultures, is important for epidemiological research. Objective: To translate and carry out the cross-cultural adaptation of the questionnaire developed by Feldmann in 2007, concerning the perceptions of adolescent patients about orthodontic treatment, into Portuguese. Methods: Initially, the equivalence of concepts and items was discussed by a group of experts who examined the items in the questionnaire. Four adolescents were interviewed using the focus group methodology. The instrument was then submitted to the following steps: two translations into Portuguese by independent translators, pre-testing of the questionnaires in 6 patients, reverse translation, review by committee and finally a pilot study with the final version. In this stage, 20 adolescents aged between 12 and 17 years, of both genders, were interviewed, evaluated at the Orthodontics Clinic of the Faculty of Dentistry of the State University of Rio de Janeiro. The questionnaire was applied to two groups: untreated adolescents and adolescents undergoing orthodontic treatment. Results: From these evaluations, the Brazilian version of the Feldmann questionnaire was produced, with administration and format appropriate to the target population. Conclusions: The translation and cross-cultural adaptation of the questionnaire into Portuguese was performed ensuring its semantic and conceptual equivalence with the original instrument and the final version was consistent in a pilot study.