Background: The aim of this study was to investigate whether short-duration adaptive servo-ventilation (ASV) therapy improves cardiac function in heart failure (HF) patients. Methods and Results: Consecutive HF patients (n=86) were divided into 3 groups: group A, ASV for a mean of ≥4h; group B, ASV for ≥1 to <4h per day; and group C, no ASV or ASV <1h. The frequency of ASV use did not significantly differ between groups A (79.3±19.2%) and B (70.9±17.4%). After 6 months, a significant increase in left ventricular ejection fraction (LVEF), significant decrease in plasma brain natriuretic peptide (BNP) and decrease in LV end-diastolic volume (LVEDV) were observed in groups A (LVEF, 5.0±8.1%; BNP, −24.9±33.7%; LVEDV, −6.2±10.1%) and B (LVEF, 3.5±5.5%; BNP, −16.5±24.6%; LVEDV, −5.1±8.2%) as compared with group C (LVEF, −1.5±6.0%, P=0.004, P=0.017; BNP, 2.8±10.2%, P=0.002, P=0.017; LVEDV, 0.8±9.1%, P=0.031, P=0.043). Significant correlation was seen between the total ASV time and changes of LVEF (r=0.369, P=0.002), BNP (r=−0.445, P<0.001), and LVEDV (r=−0.374, P=0.001). Admission rate was lower in groups A (4.1%) and B (7.1%) than in group C (25%, log-rank test; P=0.042, P=0.045). Multivariate analysis showed that the frequency of ASV use was a strong parameter for the improvement of LVEF (coefficient=0.284, standard error=0.035, P=0.019). Conclusions: Even a short-duration of ASV therapy may improve cardiac function in HF patients.  (Circ J 2012; 76: 2606–2613)