To determine which laser can be used for a vascular lesion, the different working mechanisms of the individual lasers must first be understood. The localization and diameter of the vessels to be treated define whether a certain laser is appropriate for that lesion. For teleangiectasias and port-wine stains the pulsed-dye laser works without scarring. Hemangiomas respond only when flat and superficial. Deeper lesions can only be reached with the ND-Yag laser.