Summary Background  There is no consensus on the most appropriate treatment for patients with large to giant congenital melanocytic naevi (CMN) because of the risk of melanoma development. Surgical excision followed by skin grafting or expanded skin coverage may cause unfavourable scarring. There is a balance to be achieved between minimizing the disfiguring appearance and the risk of malignant change. The pulsed dye laser (PDL) is commonly used for vascular lesions and is highly absorbed by melanin and haemoglobin. Its pulse duration is longer than that of Q-switched ruby lasers (QsRL), which can have nonspecific photothermolytic effects on surrounding nonpigmented naevus cells.

Objectives  To investigate the effectiveness of combined treatment with the PDL and QsRL for large to giant CMN.

Methods  Six patients with large to giant CMN were enrolled in this study. Treatment consisted of one pass of PDL treatment followed by one pass of QsRL treatment. Multiple rounds of treatment were applied to all patients.

Results  All patients responded to this combined regimen, and the lesional colour was effectively reduced. The mean number of rounds of laser treatment required to achieve skin lightening was 7·7. No patients suffered severe hypertrophic scarring. No cases of recurrence or malignant transformation were observed. The histological results from the patient who underwent the most laser therapy in this study showed a remarkable reduction in the number of melanocytic naevus cells after treatment.

Conclusions  This technique may enable the removal of most of the pigmented lesion and melanocytic naevus cells with minimal scarring.