The aims of this study were to investigate the medication adherence of patients on pulmonary hypertension (PH)-targeted therapies and uncover factors that might influence adherence values. Patients taking at least one specialist medicine (sildenafil, tadalafil, bosentan, ambrisentan, iloprost, epoprostenol, treprostinil) completed a Morisky Medication Adherence Scale-8 (MMAS-8) questionnaire. Participants’ MMAS-8 scores were used to estimate overall medicine adherence. Potential adherence co-factor data were collected from patient databases and hospital discharge summaries. The MMAS-8 questionnaire was completed by 263 patients (mean age = 61.6 ± 14.8 years, 70.6% women). Data from MMAS-8 showed that 47.9% reported high adherence, 40.3% moderate adherence, and 11.8% low adherence. . . . .