Patent foramen ovale (PFO) is present in about one-quarter of the population and should be considered an anatomical variant rather than a malformation. The association of PFO with cryptogenic stroke, migraine, peripheral embolism and other pathologies is still controversial. The evaluation of anatomical complexity, and particularly the long-tunnel morphology, is crucial for the assessment of the risk profile and for a targeted therapeutic management. Long-tunnel PFOs seem to be more prone to clot formation and complications related to percutaneous closure procedures. Echocardiography is the most useful method to investigate anatomical complexity, confirm and reinforce the indication to treatment, select the appropriate device and guide the PFO closure towards a successful procedure.