Objective: To study the characteristics and prognostic implications of type 2 diabetes in different heart failure entities from a nationwide perspective. Methods: This observational study comprised 30,696 heart failure patients prospectively included in the Swedish Heart Failure Registry (SwedeHF) 2003-2011 from specialist care, with mortality information available until December 2014. Patients were categorized into three heart failure entities by their left ventricular ejection fraction (heart failure with preserved ejection fraction: amp;gt; 50%, heart failure with mid-range ejection fraction: 40%-49% and heart failure with reduced ejection fraction: amp;lt;40%). All-cause mortality stratified by type 2 diabetes and heart failure entity was studied by Cox regression. Results: Among the patients, 22% had heart failure with preserved ejection fraction, 21% had heart failure with mid-range ejection fraction and 57% had heart failure with reduced ejection fraction. The proportion of type 2 diabetes was similar, approximate to 25% in each heart failure entity. Patients with type 2 diabetes and heart failure with preserved ejection fraction were older, more often female and burdened with hypertension and renal impairment compared with heart failure with mid-range ejection fraction and heart failure with reduced ejection fraction patients among whom ischaemic heart disease was more common. Type 2 diabetes remained an independent mortality predictor across all heart failure entities after multivariable adjustment, somewhat stronger in heart failure with left ventricular ejection fraction below 50% (hazard ratio, 95% confidence interval; heart failure with preserved ejection fraction: 1.32 [1.22-1.43], heart failure with mid-range ejection fraction: 1.51 [1.39-1.65], heart failure with reduced ejection fraction: 1.46 [1.39-1.54]; p-value for interaction, p = 0.0049). Conclusion: Type 2 diabetes is an independent mortality predictor across all heart failure entities increasing mortality risk by 30%-50%. In type 2 diabetes, the heart failure with mid-range ejection fraction entity resembles heart failure with reduced ejection fraction in clinical characteristics, risk factor pattern and prognosis.