We investigated the contribution of a dilated right-sided heart to roentgenographic cardiomegaly in patients with heart failure (HF) and a normal ejection fraction (EF; diastolic HF) and those with HF and a decreased EF (systolic HF). We compared the cardiothoracic ratio (CTR) on upright chest roentgenograms and major- and minor-axis dimensions of the 4 cardiac chambers on echocardiograms in patients with HF and a normal EF (> or =0.50, n = 35) and those with a decreased EF (<0.50, n = 37) and examined the correlation between the CTR and cardiac chamber dimensions. The CTR did not differ between patients with normal and decreased EF values (0.58 +/- 0.07 vs 0.60 +/- 0.06, p = 0.26). Left-side cardiac chamber dimensions were substantially smaller in patients with a normal EF than in those with a decreased EF (left ventricular minor-axis dimension, 4.4 +/- 0.7 vs 5.8 +/- 0.8 cm, p <0.001). In contrast, right-side cardiac chamber dimensions were generally similar between groups. The CTR correlated with major-axis dimensions of the right ventricle and right atrium (p <0.01 for the 2 comparisons), but not with the left-side cardiac chamber dimensions (all p values >0.05). In conclusion, the CTR predominantly reflects right- rather than left-sided heart size in patients with HF. Right-sided heart size is similar between patients with normal and decreased EF values. Thus, despite the substantial difference in left ventricular size and EF, there is substantial overlap in the CTR between patients with diastolic and systolic HFs and the CTR is unable to discriminate between groups.