Aims Women are more likely to develop heart failure with preserved ejection fraction (HFpEF) than men. We studied the relationship between sex and cardiovascular structure and function in patients with HFpEF. Methods and results The study included 279 participants from the PARAMOUNT study (57% women) with analysable baseline echocardiograms (mean age 71 years, 94% hypertensive, 38% diabetic). We assessed sex-based differences in baseline clinical characteristics and measures of cardiovascular structure/function. Coronary artery disease was less common in women than in men. Women were more obese and symptomatic, and less likely to have albuminuria. Women had higher indexed left ventricular (LV) wall thicknesses, worse diastolic function (lower Eâ€, P=0.002; higher E/Eâ€, P<0.001), while LV mass and LV volumes indexed for height2.7 were similar. Nonetheless, female sex was associated with a trend towards higher prevalence of abnormal LV geometry (defined as concentric hypertrophy, or eccentric hypertrophy, or concentric remodelling) at baseline (unadjusted P=0.028, adjusted P=0.056) and 12weeks' follow up (unadjusted P=0.001, adjusted P=0.006), but not at 36weeks' follow up (unadjusted P=0.81, adjusted P=0.99). Despite higher LV ejection fraction in women, global LV strain was similar between the sexes, while Tissue Doppler Imaging Sâ€ mitral velocity was lower in women. Both LV diastolic and systolic stiffness were higher in women than men (P<0.001), even adjusting for LV concentricity and clinical covariates. We observed no sex differences in systolic arterial-LV coupling, as women also had higher absolute arterial elastance compared with men, although this difference was not significant after adjusting for height2.7. Conclusion More pronounced diastolic dysfunction may contribute to the greater predisposition for HFpEF in women compared with men. © 2014 The Authors.