Port-wine stains (PWS) are among the most common congenital vascular malformations. Unlike capillary haemangiomas, these lesions do not involute spontaneously but rather become progressively more disfiguring as the patient ages. While benign in nature, the cosmetic deformity and attendant psychological and emotional distress prompt the majority of those afflicted to seek treatment. The pulsed dye laser (PDL) has long been considered the treatment of choice for these vascular lesions; however, very few patients achieve total clearance with PDL therapy and a significant number of lesions fail to respond at all. In order to address these recalcitrant cases, the mechanisms that contribute to treatment resistance must be understood and novel laser and light therapies must be employed. This review will address what is currently known about lesion-specific characteristics of PDL-resistant PWS as well as discuss current and future treatment options.