Epicardial fat is the visceral fat depot of the heart and is commonly increased in obese subjects. Obesity is also associated with right ventricular (RV) enlargement. Nevertheless, whether epicardial fat might be independently associated with RV morphology is unknown. I evaluated the correlation between echocardiographic epicardial fat and RV cavity size in subjects with a wide range of adiposity. Echocardiographic epicardial fat thickness and RV end-diastolic diameter (RVEDD) were assessed in 50 obese and 50 normal weight subjects. Patients with clinical conditions that could affect the RVEDD were excluded. Obese subjects had a significantly greater epicardial fat thickness and RVEDD than normal weight subjects (10 ± 4 vs 5 ± 2 mm and 22 ± 10 vs 15 ± 5, respectively; p <0.01 for both). The univariate relation between the epicardial fat thickness and RVEDD was very significant (r = 0.82, p <0.01) for overall obese and normal weight subjects. Multiple regression analysis showed that epicardial fat thickness was the best independent correlate of RVEDD (r² = 0.42, p <0.01) in overall subjects. In conclusion, increased RV epicardial fat accumulation is associated with enlarged RV cavity size.