Recent reports from pulmonary arterial hypertension (PAH) registries suggest that the mean age at diagnosis is increasing, outlining a growing proportion of elderly male patients. As a consequence, the classical description of the disease is shifting and may no more be described as a rare disease typically affecting young women. Potential explanations of this changing picture may include an aging of populations in western countries, the increase in life expectancy and the growing awareness of PAH and emergence of potential efficient treatments. Diagnostic workup of severe pulmonary hypertension (PH) in the elderly should be performed in such a way as to discriminate between the expected consequences of aging, pulmonary vascular disease, and other frequent causes of secondary PH (left heart failure or lung disease). Careful exploration by right heart catheterization is mandatory, but special attention should be paid to several pitfalls specific to this procedure in this age group. This is a matter of concern as clinical trials that aim to study new specific drug therapy for PAH might be biased by the inclusion of misdiagnosed patients. The aim of this review is to highlight the main difficulties in diagnosing PAH in the elderly and to propose a practical approach to distinguish PAH from the other frequent causes of PH in this population.