Abstract Introduction Evaluation of tricuspid annulus (TA) has many challenges due to its complex three-dimensional shape. The 3D-echocardiography is a gold standard method for accurate assessment of tricuspid valve (TV). Studies investigating TV geometry in different aetiologies of tricuspid regurgitation (TR) are still scarce. Aim The aim was to clarify the TV geometry characteristics in different aetiologies of functional TR (FTR). Methods Prospective observational cohort study enrolled 107 patients with functional moderate or severe TR and 10 healthy controls. FTR patients were divided into two groups according to the different aetiology of FTR: 1. TR caused by dominant left-sided valvular pathology (LSVP) – 68 patients (pts); 2. TR caused by precapillary pulmonary hypertension (PH) (invasively measured pulmonary capillary wedge pressure <15 mmHg) – 39 pts. Pts with ischemic heart disease (assessed by coronary angiography) were excluded from the analysis. The 3D-transthoracic echocardiography was performed and included the following parameters: the systolic and diastolic 4-chambers (septal–lateral), 2-chambers (anterior–posterior), major axis TA diameters, TA area, perimeter, leaflets tenting height and volume. All parameters have been indexed to body surface area. The 3D TV analysis was made using 4D Auto TVQ quantification software package (GE Healthcare, USA). The statistical analysis was performed using SPSS statistical software. Results Study cohort included 66% females; mean age was 65±11 years. TR severity, measured quantitatively, did not differ between FTR groups (ERA – 32±18 in LSVP vs 35±18 mm2 in PH group, p=0.219). The distribution of echocardiography parameters in study groups are shown in Table 1. All the 3D TV parameters were increased in both FTR groups when compared to controls. Precapillary PH was associated with larger leaflets tenting height, volume, and more increased indices of TA systolic and diastolic septal-lateral and major axis diameters. LVSP aetiology was associated with higher TA sphericity index. Conclusions Tricuspid valvular geometry differs between different aetiologies of functional TR. The implementation of 3D echocardiography is useful in the determination of TV geometry changes and might provide valuable tools in the evaluation of patients with functional TR. Funding Acknowledgement Type of funding sources: None.