The University of Lausanne looked at 25 studies involving 1.2m patients.
They found smokers had a 44% increased risk of type 2 diabetes compared with non-smokers - with the risk rising with the number of cigarettes smoked.
The Journal of the American Medical Association study found the increased risk for those who smoked at least 20 cigarettes a day rose to 61%.
Smoking may be one of the pieces missing from the diabetes jigsaw which could help us to identify who is at higher risk Douglas Smallwood Diabetes UK
For lighter smokers the risk was 29% higher than for a non-smoker.
The increased risk of developing diabetes in former smokers was 23%.
The researchers said: "We conclude that the relevant question should no longer be whether this association exists, but rather whether this established connection is causal."
They admitted that the research did not prove that smoking contributed to the development of diabetes.
But they suggest the fact that people who smoked most heavily were most at risk is significant.
Previous research has linked smoking to insulin resistance - a condition which often leads to diabetes.
Source - BBC