Background: In patients with pulmonary arterial hypertension, substantial clinical benefits have been reported with the use of phosphodiesterase-5 inhibitors(PDE5i) . Moreover, some studies would have proven useful effects of PDE5i also on the clinical picture of the pulmonary hypertension(PH) secondary to left-sided chronic heart failure(CHF). Methods: We performed a meta-analysis comprising randomized controlled trials ( RCTs) which had compared PDE5i ( mostly sildenafil) with placebo in CHF patients. Results: 14 studies, including 928 patients overall , were admitted to the meta-analysis. In heart failure with reduced left ventricular ejection fraction(HFREF), PDE5i, compared to placebo, significantly improved the composite of death and hospitalization (OR= 0.28; 95% CI: 0.10 to 0.74). They also improved peak VO2 (difference in means[MD]: 3.76; 95% CI: 3.27 to 4.25), six-minutes walk distance ( (6MWD)( MD, 22.7 meters ; 95% CI, 8.19 to 37.21) and pulmonary arterial systolic pressure (MD: -11.52 mmHg; 95% CI: -15.56 to -7.49). Conversely, in CHF with preserved left ventricular ejection fraction ( HFpEF), PDE5i were shown not to yield any beneficial effect concerning the investigated endpoints. Conclusions: In HFREF, PDE5i were shown to improve the composite of death and hospitalization, as well as exercise capacity and pulmonary hemodynamics. Conversely, in HFpEF, no significant clinical, ergospirometric or hemodynamic betterment was achieved using PDE5i treatment.