This study sought to examine the relationships between right ventricular (RV) function and geometry, morbid obesity with and without the metabolic syndrome, and the effect of long-term weight loss. Obese (n = 153, BMI 41.2 ± 8.7 kg/m(2)) and healthy non-obese control subjects (n = 38, BMI 25.5 ± 3.3 kg/m(2)) of similar age and gender distribution were prospectively studied during the course of a 1-year weight reduction program with echocardiography at baseline and after one year of follow up. Function and geometry of the right heart were evaluated by tricuspid annular plane systolic excursion (TAPSE), tricuspid annular systolic velocity (TDI S'), RV myocardial performance index (TEI), RV end-diastolic (RVEDD) and end-systolic diameter (RVESD), area of the right atrium (RAA), and systolic pulmonary artery pressure (PAP). Whereas parameters of systolic and diastolic LV function were significantly worse in the obese subjects than those in the non-obese subjects (EF 66 ± 6 versus 69 ± 6%, P = 0.004; E/E' 7.4 ± 2.5 versus 6.3 ± 2.6, P = 0.010), parameters of RV function (TAPSE 25.6 ± 4.5 versus 25.1 ± 3.5 mm, P = 0.528; TDI S' 13.5 ± 2.9 versus 13.8 ± 2.9 mm/second, P = 0.553; TEI 0.25 ± 0.13 versus 0.28 ± 0.09, P = 0.283) as well as geometry measurements were comparable between the obese and non-obese participants and also in obese subjects with full blown metabolic syndrome. Additionally, successful weight reduction did not alter the RV parameters. Nevertheless, in the few obese subjects with RV dysfunction (n = 7), metabolic syndrome parameters were more pronounced than in obese with normal RV function.Morbid obesity with and without the metabolic syndrome is accompanied by an impaired LV systolic and diastolic function. In contrast, RV function appears to be less affected by obesity independent of the presence of the metabolic syndrome.