Summary Background  Pulsed‐dye laser (PDL)‐mediated photothermolysis is the current standard treatment for port‐wine stain (PWS) birthmarks. Vascular‐targeted photodynamic therapy (PDT) might be an alternative for the treatment of PWS. Objectives  To compare clinical outcomes of PDT and PDL treatment of PWS. Methods  Two adjacent flat areas of PWS lesions were selected from each of 15 patients (two male and 13 female; age 11–36 years) and randomly assigned to either single‐session PDL or PDT. PDL was delivered using a 585‐nm pulsed laser. PDT was carried out with a combination of haematoporphyrin monomethyl ether (HMME) and a low‐power copper vapour laser (510·6 and 578·2 nm). Clinical outcomes were evaluated colorimetrically and visually during follow‐up. Results  A total of nine red PWS lesions and six purple PWS lesions were treated. For red PWS, colorimetric assessment showed that the blanching rates of PDL and PDT at 2 months ranged from −11% to 24% and 22% to 55%, respectively. For purple PWS, blanching rates of PDL and PDT ranged from 8% to 33% and 30% to 45%, respectively. Overall, there was a significant difference between the blanching effect of single‐session PDL treatment and a single‐session PDT treatment. Conclusions  This side‐by‐side comparison demonstrates that PDT is at least as effective as PDL and, in some cases, superior. The true value of PDT for the treatment of PWS deserves further investigation. What’s already known about this topic? •  To date, several Chinese studies of photodynamic therapy (PDT) for port‐wine stains (PWS) indicate that this therapeutic modality is effective and safe for the treatment of PWS of all colour and in all ages. •  Our retrospective study suggested that PDT is as effective as pulsed‐dye laser (PDL) treatment for pink PWS and more effective than PDL for purple PWS. What does this study add? •  This is the first side‐by‐side and quantitative comparison of PDL and PDT. •  The findings reported here confirm that PDT is at least as effective and safe as PDL, if not superior to, for the treatment of red and purple flat PWS.