The prognosis of malignant melanoma depends on the thickness of the tumour. In this study, we analysed the trends in Breslow thickness in 63 patients referred to our institution, a tertiary dermatology referral centre. The mean thickness of melanoma was 0.31 mm, which was lower than the national average of 1.10 mm. There was a significant trend towards increased melanoma thickness with increasing age, with a rate of 0.24 mm (95% CI 0.12–0.37) for each additional 10 years of age above the age of 20 years. This trend was only apparent in cases of self-diagnosed melanomas; the thickness of tumours diagnosed by a dermatologist did not show any dependence on patient age. As the mortality from melanoma increases with age, this study suggests that dermatologists should include older people in screening programmes for melanoma.