Thin melanomas are killing more Australians than thick ones, demonstrating that prevention is the only reliable defence against the skin cancer.

Thin melanomas kill more people than thick ones, showing that prevention is the only reliable defence against the most dangerous form of skin cancer, researchers say.

Generally, there is a greater chance of melanomas spreading as they become thicker.

But a study published on Tuesday in the US-based Journal of Investigative Dermatology found thin melanomas of less than one millimetre killed more Queenslanders over two decades than melanomas thicker than four millimetres.

"This research highlights the message that all melanomas are potentially dangerous," said Professor David Whiteman of Brisbane-based QIMR Berghofer Medical Research Institute.

A team led by Prof Whiteman studied data from the Queensland Cancer Registry, which recorded over 4000 melanoma deaths between 1990 and 2009.

They found that from 1990 to 1994, thin melanomas accounted for 14 per cent of all melanoma deaths, and that increased to 23 per cent from 2005 to 2009.

Thick melanomas accounted for 11 per cent of melanoma deaths in the first five years of the study period, and increased to 14 per cent in the last five.

"It's a reminder that we should be doing everything in our power to try to prevent melanomas in the first place by slip, slop, slap and keeping out of the sun," said Prof Whiteman.

Melanoma kills 15,000 Australians every year and Queensland has the world's highest rates of the malignancy.

Copyright AAP 2014.