Photodynamic therapy (PDT) has poor therapeutic outcomes for the treatment of port-wine stain (PWS) lesions with long drug-light intervals (DLIs). This letter investigates the possibility of improving the treatment efficacy through increasing the laser power density using a computer simulation and a cock comb model. The computational model includes a Monte Carlo simulation for the laser distribution and a calculation of the singlet oxygen concentrations (1O2). Both simulation and experimental results show that increasing the power density from 100 to 140 mW/cm2 not only improves the PDT efficacy, but also results in the unwanted skin damage.