Objective To analyse clinical, serological and sonographic differences between rheumatoid arthritis (RA) and polyarticular psoriatic arthritis (PsA) patients on anti-TNF therapy in clinical remission. Methods Angiogenic and proinflammatory cytokine serum levels were determined by multiplex ELISA in patients with RA and PsA in clinical remission (DAS28-ESR3.2) and healthy controls. Ultrasound (US) scans were made of both wrists and hands. Results 30 RA and 47 PsA patients in remission, 22 active RA patients and 20 healthy controls were included. PsA patients had significantly lower disease activity according to DAS28-ESR (p=0.006) but not according to DAS28-CRP (p=0.319), and lower serum levels of proinflammatory and angiogenic cytokines than RA patients in remission. PsA patients had cytokine levels similar to healthy controls, while RA patients in remission had similar levels to those of active RA patients. Globally, 31 (40.25%) patients in remission had a PD signal and 12 had SH >= 2 plus PD [ I PsA vs. 11 RA (p=0.0001)], meeting the criteria for ultrasound-defined active synovitis (UdAS). Patients with UdAS had significantly higher levels of IL-6, IL-20, PIGF and SDFI. More PsA patients were on tapered doses of anti-TNF (63.8%), and more frequently as monotherapy (72.3%), compared with RA patients (26.6% and 20%, respectively). Conclusion Polyarticular PsA patients in remission had lower levels of local (US synovitis) and systemic inflammation than RA patients in remission, even though a significantly higher percentage of PsA patients were on tapered doses of anti-TNF, mainly in monotherapy.