Objective. To study, in a real-life setting, the construct validity, the reliability, and the interpretability of the 12-item Psoriatic Arthritis Impact of Disease (PsAID-12) questionnaire in patients with psoriatic arthritis (PsA). Methods. In 144 consecutive patients with PsA ( 81 men and 63 women, mean age of 51.4 +/- 12.8 yrs, and 77 receiving biologic treatment), the PsAID-12 and other patient-reported outcomes ( PRO) were collected, such as the Dermatology Life Quality Index. Each patient underwent articular and skin assessment. Results. Construct validity: Factor analysis revealed a 2-factor result defined as the PsAID Symptom Score and the PsAID Skin Score. In determining convergent validity, significant correlations were found between the PsAID-12 and the clinical Disease Activity index for Psoriatic Arthritis (cDAPSA;. rho = 0.867, p < 0.0001). Multivariable analysis showed that the PsAID-12 is determined by the articular disease activity ( cDAPSA, p < 0.0001), severity of psoriasis (PsO; physician's global assessment, p < 0.0001), and the presence of a coexisting fibromyalgia ( FM; p < 0.0001). Reliability: Cronbach's alpha coefficient was 0.93 for the total PsAID-12. Interpretability: Applying the cDAPSA categorization of disease activity states, the PsAID-12 cutoff values resulted in 1.4 between remission and low disease activity (LDA), 4.1 between LDA and moderate disease activity (MDA), and 6.7 between MDA and high disease activity. Conclusion. The PsAID-12 is an excellent PRO to evaluate the effect of PsA. It should be carefully handled in patients with coexisting FM.