Cognitive distortions are central to contemporary clinical theory and practice, yet psychometric evidence for the Persian Cognitive Distortions Questionnaire (CD-Quest) has been limited. This study evaluated the psychometric properties of the Persian CD-Quest in Iranian adults. Participants (N = 567; 18–60 years) were recruited in 2023 from Arak, Iran, using quota-based stratification by gender and recruitment site (ten high-traffic urban locations, e.g., city bazaar, main square, university, service centers). Measures included the CD-Quest, Automatic Thoughts Questionnaire, and General Health Questionnaire. Analyses combined Classical Test Theory (CTT) and Item Response Theory (IRT). CTT results showed acceptable item–total correlations (≥0.30). IRT supported unidimensionality and favored the generalized partial credit model; item parameters (discrimination and ordered thresholds) were satisfactory. The test information function indicated greatest precision at moderate-to-high levels of the latent trait (peak around θ ≈ 1.70; high-information band θ ≈ 0.34–3.02); marginal reliability was ρ = 0.701. Gender-based DIF (Wald/Lord χ2 , Holm–Bonferroni) was not detected, supporting item-level measurement invariance (women vs. men). Findings suggest the Persian CD-Quest was psychometrically sound and informative for clinical screening and research in Iranian adults, thereby advancing cross-cultural assessment of self-related distorted thinking within Beck’s cognitive framework while enabling valid comparisons across gender.
