Abstract Objectives To study the association of clinical and/or ultrasound variables with patients′ (PGA) and physicians′ (EGA) global assessment of disease activity in Psoriatic Arthritis (PsA). The correlation of these parameters with the discordance between PGA and EGA, as well as with PGA/EGA changes over 6 months was also investigated. Methods Prospective study of 83 consecutive PsA patients with 2 visits scheduled 6 months apart. All patients underwent the following assessments: tender (TJC) and swollen joint count (SJC), PASI, dactylitis and Leeds enthesitis index. PGA, patients′ level of pain (pain VAS), EGA, and HAQ were also recorded. Grey scale (GS) and Power Doppler (PD) ultrasound were performed at 68 joints (evaluating synovia and tendons) and 14 entheses. Regression analyses were performed to assess the association of these variables with PGA and EGA. Two new variables ‘PGAminus EGA′ and ‘PGAchange-EGAchange′ were developed to explore the discrepancy between PGA and EGA and the consistency of PGA/EGA changes over time, respectively. Results The parameters explaining most of PGA and EGA variability were pain VAS (30.5%) and SJC (48.5%), respectively. The correlation between EGA and joint counts was stronger in patients with high versus low levels of ultrasound verified inflammation. PGAminus EGA was mainly explained by pain and SJC. Pain was the most important predictor of PGA change whereas TJC and HAQ were more closely associated with EGA changes. ‘PGAchange-EGAchange′ was linked to pain and SJC. Ultrasound scores were not linked with either of these variables. Conclusions Pain VAS and joint counts are the most important clinical parameters explaining patients′ and physicians′ perception of disease activity, whereas the correlation of active inflammation as verified by sonography with these factors is limited.