Objective: According to Bernoulli Equation, systolic pulmonary artery pressure is obtained echocardiographically by adding estimated right atrial pressure (RAP) to the multiply of square of tricuspid regurgitation flow rate by four. RAP is estimated based on inferior vena cava (IVC) diameter and collapse. Our objective is to investigate usability of coronary sinus(CS) diameter and collapse, measured by echocardiography for estimating RAP. Methods: Our study is a single center, prospective study. 136 patients, over 18 years of age and without exclusion criteria, who admitted to Akdeniz University Hospital Cardiology Department between March 2017 and March 2018 and were scheduled to undergo right heart catheterization for any reason were included study. Results: Patients were divided into two groups as invasively measured RAP ≥10 mmHg (n: 57) and RAP <10 mmHg (n: 79). In group with RAP ≥10 mmHg, maximum IVC and CS diameter were higher than group with RAP <10 mmHg, IVC and CS collapse indices were lower (p <0.001). Optimal cut-off value for maximum IVC diameter was 19.6 mm (sensitivity 63.2%, specificity 87.3%), for IVC collapse index was 46.1 (sensitivity 75%, specificity 79.7%), for maximum CS diameter was 11 mm (sensitivity 64.9%, specificity 77%), for CS collapse index was 39.2 (sensitivity 75.4%, specificity 88.6%). Conclusion: Significant relationship was found between invasively measured RAP and maximum IVC diameter, collapse index and maximum CS diameter and collapse index. Results of CS parameters were as significant as results of IVC parameters therefore it shows that CS can also be used for estimating RAP.