Background Estimates of psoriatic arthritis (PsA) prevalence among psoriasis patients vary widely (5-40%). The time to development of PsA in patients with plaque psoriasis also remains unclear. Objectives To examine whether length of time since diagnosis of psoriasis affects risk of developing PsA, and to assess differences in quality of life (QoL), work-related issues, comorbidities and healthcare resource utilization (HCRU) for patients with PsA vs. psoriasis. Methods This large cross-sectional observational study was conducted in the UK, Italy, France, Spain and Germany in 2006. Dermatologists who actively treated patients with psoriasis recruited 10 consecutive patients with psoriasis. Presence of PsA, body surface area (BSA) affected with psoriasis and HCRU were recorded; patients completed EUROQoL (EQ5D) and employment disadvantages questionnaires. Results Patients with psoriasis (n = 1560) included 126 with PsA. Ninety per cent of these patients with PsA were seen by dermatologists who involved a rheumatologist in the care of their patients with PsA. Survival analysis indicated that the incidence of PsA among psoriasis patients remained constant (74 per 1000 person-years), while the prevalence increased with time since diagnosis of psoriasis, reaching 20.5% after 30 years. In addition, those with high BSA currently affected by psoriasis were more likely to have developed PsA (P <0.028). PsA patients reported reduced QoL compared with psoriasis patients (EQ5D score: 0.56 vs. 0.82: P <0.0005), as well as more work problems. PsA patients were more likely to be hospitalized (0.27 ± 0.84 vs. 0.14 ± 0.71 per year; P <0.0005) and have additional comorbidities than those without PsA. Conclusions The incidence of PsA was constant after initial diagnosis of psoriasis, leading to a higher prevalence of concomitant PsA over time. PsA is associated with decreased QoL and increased work-related problems, HCRU and comorbidities. Dermatologists should screen for PsA in their patients, especially long-standing patients who did not initially present with PsA. © 2009 European Academy of Dermatology and Venereology.