OBJECTIVES: Psoriatic arthritis (PsA) and rheumatoid arthritis (RA) are inflammatory arthritis with significant impact on patients' health related quality of life (HRQL). The main goal of this study is to analyse the HRQL measures in these conditions. METHODS: Two cross sectional questionnaire surveys of consecutive patients with PsA (2008) and with RA (2004) were conducted in the same rheumatology outpatient centres in Hungary. Patients filled in the generic EQ-5D and the disease specific Health Assessment Questionnaire (HAQ), Psoriatic Arthritis Quality of Life Questionnaire (PsAQoL) / Rheumatoid Arthritis Quality of Life Questionnaire (RAQoL). Assessing construct validity, patients were grouped by disease severity based on the yearly number of admissions to hospital, being on disability pension, use of devices and resort to help from others for everyday activities. The magnitude of difference between groups, the effect size was calculated as the standardized mean difference. Convergent validity was investigated by calculating the Spearman's correlation between clinical scale variables and HRQL instruments. RESULTS: A total of 183 AP and 255 RA patients were enrolled. HRQL instruments' scores were closer to the worse end of scales in case of severe PsA and RA, the highest effect size of each HRQL instrument was detected at use of home care. Strong correlations (rho>0.5) were observed between the EQ-5D, the PsAQoL / RAQoL, the HAQ disability score, the patient pain and global VAS. Disease duration of PsA and RA correlated weakly (rho<0.29) with all the HRQL instruments. CONCLUSIONS: Our results confirm the good ability of EQ-5D, HAQ, PsAQoL/RAQoL to describe health state in PsA and RA. Our study is the first to establish the correlation of HRQL instruments in PsA.