Purpose: In 2000, it was identified the BMPR2 gene involved in the development of pulmonary hypertension (PH). More than 200 mutations have been described in this gene and, although, anatomical and histological changes are similar in patients with and without mutations, differences in clinical expression have been found. The aim of this study was to define the prevalence of BMPR2 mutations in a Spanish population with idiopathic or hereditary PH and describe differences in clinical expression. Methods: We included patients with idiopathic or hereditary PH followed up between December 2011 and January 2012. We performed a BMPR2 genetic study, using multiple ligation-dependent probe amplification and DNA sequencing, patients were grouped into those who had mutation or not. Then, we made a retrospective analysis of clinical, echocardiographic, hemodynamic and respiratory parameters at time and at one year of the diagnosis. Results: A total of 61 patients were included, 52 idiopathic and 9 hereditary PH. BMPR2 mutation was detected in 14 patients, 8 patients with idiopathic form, prevalence in this subgroup was 15.4%, and 6 in patients with hereditary form, prevalence was 66.7%. We found 13 different mutations (1 exon2 deletions, 1 deletion of the whole allele, 1 exon2 duplication, 7 single base substitution and 3 microdeletions), 5 were not previously described. There was no difference in the time of follow up in each subgroup. Patients with BMPR2 mutation were significantly younger (32.5±9.6 years vs 42.8±13.3 years), none of them had a positive response in the acute vasodilator test, and respiratory function test were significantly better (forced vital capacity 96.8±7.8 vs 88.3±14.3, expiratory flow in one second 99.1±9.2 vs 85.4±14, 4 and carbon monoxide diffusing 87.8±12.5 vs 76.1±18.8), although there were no differences in the arterial pressure of oxygen or carbon dioxide. There were no differences in clinical presentation, distance in the 6 minutes walking test, echocardiographic or hemodynamic parameters at time or at one year of the diagnosis. Conclusions: The prevalence of BMPR2 gene mutation in our series was 15.4% in idiopathic and 66.7% in hereditary PH. We found 13 different mutations, 5 were news mutations. BMPR 2 mutation is associated with debut at younger ages, no response in the pulmonary vasodilator testing and better respiratory function. Continuing studies of BMPR2 gene is necessary because it involves expanding the number of known mutations, found differences in the clinical expression and the possibility of genetic counseling in this population.