Background: Efficacy of pulmonary arterial hypertension (PAH)-specific therapy may differ among the patients depending on the PAH aetiology. Aim: To compare the real-life efficacy of PAH-specific therapy between non-congenital heart disease (non-CHD) and CHD groups of PAH patients and to determine whether an early clinical response has an impact on prognosis. Methods: Clinical data from 41 PAH patients, 21 non-CHD and 20 CHD patients, were included in the study. The WHO functional class (WHO-FC), 6-minute walk dis tance (6MWD) and NT-proBNP serum level were compared at baseline and after 1 and 7 months of PAH-specific treatment. Only patients with unmodified PAH-specific therapy during 7-month follow-up were enrolled in the study. Results: Baseline characteristics revealed higher WHO-FC and increased [loge ]NT-proBNP levels (7.74 ±1.05 vs 6.51 ±1.48; p = 0.008) in non-CHD vs. CHD patients; baseline 6MWD was similar in both groups (283.3 ±148.5 m vs 339.2 ±114.7 m). Clinical improvement by at least one WHO-FC after 1-month treatment was observed more frequently in non-CHD (55%) when compared with CHD patients (25%, p = 0.04) and was comparable (50% vs 50%) after 7-month observation. Non-CHD patients, who did not improve within 1 month of treatment were unlikely to achieve improvement after 7 months. The 6MWD increased during the first month of treatment in non-CHD (p=0.009) and in CHD patients (p=0.006) when compared to baseline values and remained at this level after 7 months of treatment. [Loge ]NT-proBNP levels markedly declined only in non-CHD patients, who had an improvement in WHO-FC (8.0 ±1.0 vs 7.4 ±1.1, p = 0.04) in the first month. In CHD patients, the decrease in [loge ]NT-proBNP level was seen (6.5 ± 1.5 vs 6.1 ±1.5, p = 0.04) only within a 1-month observation. Conclusion: Efficacy of 1-month PAH-specific therapy is aetiology-dependent and determines clinical outcome in patients with PAH.