Objective To evaluate right atrial (RA) structure and function of different left ventricular geometry in patients with obstructive sleep apnea syndrome(OSAS) by real-time three-dimensional echocardiography (RT-3DE). Methods One hundred and ninety-nine patients with habitual snoring were diagnosed as OSAS by polysomnography with apnea hypopnea index ≥5/h. Fifty gender, age matching healthy people were selected as control group. Blood pressure and general clinical characteristics were collected and echocardiography was performed next morning. On the basis of left ventricular mass index, relative wall thickness, left ventricular end-diastolic diameter, patients were divided into 6 groups: normal geometry (NG), concentric remodeling (CR), eccentric non dilated hypertrophy (ND-EH), concentric non dilated hypertrophy (ND-CH), eccentric dilated hypertrophy (D-EH), and concentric dilated hypertrophy (D-CH). Full volume images at apical four-chamber view were collected. Right atrial volume-time curve, RA maximum volume (RAVmax), RA minimum volume (RAVmin), RA pre-contraction volume (RAVpre-a) were analyzed with QLab workstation. Following parameters including RA total emptying volume (RA TotEV), RA total emptying fraction (RA TotEF), RA passive emptying volume (RA PassEV), RA passive emptying fraction (RA PassEF), RA active emptying volume (RA ActEV), RA active emptying fraction (RA ActEF) were calculated. All structural parameters were corrected by BSA. Results ①RA structural parameters: compared with control and NG groups, RAVmax, RAVmin, RAVmin/BSA, RAVpre-a and RAVpre-a/BSA were increased in ND-EH, ND-CH and D-(CH+ EH) groups (P<0.05). Compared with control, NG and CR groups, RAVpre-a and RAVpre-a/BSA were increased in ND-EH, ND-CH and D-(CH+ EH) groups, RAVmax, RAVmax/BSA, RAVmin, RAVmin/BSA, RAVpre-a and RAVpre-a/BSA were increased in ND-CH and D-(CH+ EH) groups(P<0.05). Compared with control, NG, CR and ND-EH groups, RAVmax, RAVmax/BSA, RAVpre-a and RAVpre-a/BSA were increased in ND-CH, D-(CH+ EH) groups, RAVmin and RAVmin/BSA were increased in D-(CH+ EH) group (P<0.05). Compared with control, NG, CR, ND-EH and ND-CH groups, RAVpre-a and RAVpre-a/BSA were increased in D-(CH+ EH) group (P<0.05). ②RA reservoir function parameters: compared with control, NG and CR groups, RA TotEV was increased in ND-CH and D-(CH+ EH) groups (P<0.05). Compared with control, NG, CR and ND-EH groups, RA TotEV was increased in D-(CH+ EH) group (P<0.05). ③RA conduit function parameters: compared with control, NG and CR groups, RA PassEF was decreased in ND-EH, ND-CH and D-(CH+ EH) groups, RA PassEV was decreased in ND-CH and D-(CH+ EH) groups(P<0.05). Compared with control, NG, CR and ND-EH groups, RA PassEV was decreased in D-(CH+ EH) group, RA PassEF was decreased in ND-CH and D-(CH+ EH) groups (P<0.05). ④RA pump function parameters: compared with control, NG and CR groups, RA ActEF were increased in ND-CH and D-(CH+ EH) groups (P<0.05); Compared with control, NG, CR and ND-EH groups, RA ActEV was increased in ND-CH and D-(CH+ EH) groups (P<0.05). Conclusions Different left ventricular geometric patterns have different RA structure and function in OSAS, patients with ND-CH and D-(CH+ EH) have worse RA structure and function. The results of this study suggested that the clinical need to pay attention to the RA structure and function of OSAS patients with dilated LVH. Key words: Echocardiography, real-time three-dimensional; Sleep apnea, obstructive; Left ventricular geometric patterns; Atrial function, right