Background: Early recognition of Camptodactyly-arthropathy-coxa vara-pericarditis (CACP) syndrome is very important for counseling and avoiding unnecessary treatment with anti-rheumatic drugs including biologic agents. Objective: to evaluate utility of ultrasonography in CACP syndrome patients and to compare the findings of the wrist and metacarpophalangeal joints with those in JIA patients. Materials and Methods: The study cohort consisted of children with CACP syndrome and JIA with a poly-articular course. Each patient completed the same assessment: clinical examination of six joints (wrist, 2nd and 3rd metacarpophalangeal joints bilaterally), laboratory assessment, conventional radiography, and ultrasonography of the above-mentioned six joints. Ultrasonography assessment was performed in the same day as clinical and laboratory assessment. Results: A total of 24 patients have completed the evaluation: 19 JIA and 5 CACP syndrome patients with a total of 144 assessed joints, with each patient having completed the same assessment. Most patients had synovial membrane thickening. However, synovial proliferation was more prominent in CACP syndrome (26/30) compared to JIA patients (56/114) (P 0.0002). Interestingly, all CACP syndrome patients showed normal vascularity of the synovium as by color Doppler, while 25% of the assessed joints in JIA patients had increased synovial vascularity (P 0.0025). Joint effusion and bone erosion were more frequent in JIA patients compared to CACP syndrome. However, the difference was not statistically significant. Conclusion: Our findings suggest that ultrasonography is probably beneficial in differentiating inflammatory arthritis from non-inflammatory arthropathy.