Riociguat is a novel soluble guanylate cyclase stimulator that is approved for the treatment of patients with pulmonary arterial hypertension (PAH) and patients with inoperable chronic thromboembolic pulmonary hypertension (CTEPH) or persistent/recurrent CTEPH after pulmonary endarterectomy (PEA). As riociguat is a relatively new drug, experience of its use in clinical practice is limited, especially in patients who would not have met the inclusion criteria for the pivotal Phase III clinical trials, PATENT-1 and CHEST-1. This article shares our initial practical and clinical experience in switching patients with PAH and CTEPH from the phosphodiesterase type-5 inhibitor sildenafil to riociguat, based on three selected case reports of patients who discontinued sildenafil therapy owing to side effects or disease progression (one patient with idiopathic PAH and two patients with persistent/recurrent CTEPH after PEA). Two cases illustrate our experience with direct switch from sildenafil to riociguat (6-8 h between the last sildenafil dose and the first riociguat dose), and one case illustrates switch to riociguat in a patient who underwent treatment with other PAH-specific therapies between stopping sildenafil and starting riociguat. Symptoms improved with riociguat therapy in two cases; in the third case the patient experienced worsening symptoms 1 month after initiating riociguat and was switched back to sildenafil. These case experiences contribute practical information to assist clinicians in the switch from sildenafil to riociguat therapy in patients with PAH or CTEPH.