A moderate increase in cancer risk has been shown in diabetic patients and in individuals with abnormal glucose tolerance, mainly for digestive sites, independently of obesity, with in contrast, a protective effect for prostate cancer. Insulin-resistance with compensatory hyperinsulinemia, and elevated levels of circulating growth factors are usually considered to be the link between cancer and hyperglycaemia, through activated cell proliferation. Treatments inducing elevated plasma insulin seem to increase cancer risk but insulin-sensitizers (metformine, thiazolidinediones) seem to reduce cancer risk. In 2009, there was a controversy on the specific action of glargine insulin to increase cancer risk, from an observational study in Germany, which accumulated a number of methodological pitfalls. There was no confirmation of these results in the three other European studies commissioned by Diabetologia, to validate or to refute the results. The recent interest for cancer in the diabetes community should not distract from appropriate management of diabetic patients to prevent cardiovascular diseases, as the risk for death from macrovascular complications is higher than death from cancer in type 2 diabetic patients. Greater public awareness about healthy lifestyles (diet, physical activity) is needed at the general population level to prevent these two major increasing public health issues, diabetes and cancer, as well as obesity, a risk factor for both of these diseases.