Introduction
The Cognitive Distortions Questionnaire (CD-Quest) is an instrument that identifies logical errors or cognitive distortions and is used in trial-based cognitive therapy (TBCT). However, it had previously only been available for adults.

Objectives
To develop and validate a version of the CD-Quest for teens (CD-Quest-T) aged 11 to 17 years and test its psychometric properties.

Method
A total of 299 schoolchildren participated in the investigation. After content validity was assessed, the language was adapted for the target age group, and the length of the instrument was reduced to eight items (from the initial 15). Five cognitive therapists analyzed the content and structure of the items. Finally, to investigate the construct validity of the CD-Quest-T, the instrument was divided into a full scale and two subscales, which measure the frequency of the distortions and the intensity attributed to them, respectively.

Results
The overall internal consistency of the scale was α = 0.77, whereas subscale indices were α = 0.75 for the frequency scale and α = 0.73 for the intensity scale. Results from exploratory factor analysis and concurrent validity analysis indicated that the CD-Quest-T items have good psychometric properties and generate scores reliably.

Conclusion
The psychometric properties of the CD-Quest-T demonstrate its adequacy for measurement of cognitive distortions in adolescents.