Abstract Background Pulmonary hypertension results in clinical deterioration and increases mortality risk in patients with lung disease (LD), including chronic obstructive pulmonary disease, interstitial lung disease and combined pulmonary fibrosis and emphysema. Though acute vasoreactivity testing predicts long term-survival of patients with pulmonary arterial hypertension (PAH), its clinical impact for patients with pulmonary hypertension associated with LD (LD-PH) remains unknown. Purpose The purpose of this study is to clarify the clinical impact of acute vasoreactivity testing using inhaled nitric oxide for severe LD-PH. Methods We retrospectively reviewed 65 consecutive patients with LD-PH between January 2014 and December 2022; 48 patients (73 [68–78] years; males, 81%; median follow-up period 23 [7–35] months) with severe pulmonary hypertension who underwent acute vasoreactivity testing were included. We divided the patients based on a median pulmonary vascular resistance (PVR) response (−15%) in acute vasoreactivity testing into the high-responder (PVR response ≦−15%) and the low-responder (PVR response >−15%) groups. Results Acute vasoreactivity testing significantly decreased mean pulmonary arterial pressure (mPAP) (from 41 [34–48] to 36 [31–40] mmHg, P<0.01) and PVR (from 10.7 [8.3–13.8] to 8.9 [6.6–11.4] Wood units, P<0.01). The high-responder group had better long-term survival than the low-responder group (P = 0.03). Univariate Cox regression analysis showed that the prognostic factors for better survival included younger age, high-responder to acute vasoreactivity testing, and PAH-specific therapy (P <0.01, 0.04, 0.03, respectively). There were correlations between the PVR response at acute vasoreactivity testing and improvement in mPAP (R=0.40, P=0.03) or PVR (R = 0.47, P <0.01) with PAH-specific therapy. Conclusions PVR response at acute vasoreactivity testing was associated with better long-term survival and haemodynamic improvement with PAH-specific therapy. Acute vasoreactivity testing may be useful to predict the responders to PAH-specific therapy and long-term survival in patients with severe LD-PH.