Study leader Kari Hemminki at Helmholtz Association of German Research Centres in Heidelberg said the researchers could only speculate about the causes.
"Possibly, a lower level of male sex hormones in diabetics may be among the factors that are responsible for this," Hemminki said in a statement.
Hemminki and colleagues studied the cancer incidence in 125,126 Swedish citizens hospitalized due to type 2 diabetes complications as well as those of the general population in Sweden.
They also found higher risks of several cancers in those with type 2 diabetes -- very significantly for pancreatic cancer and liver cell cancers.
Diabetics also had double the risks of cancers of the kidneys, thyroid, esophagus, small intestine and nervous system.
The study, published in The Oncologist, also looked at whether the risk was higher in hospitalized diabetic patients because their tumors were found earlier due to routine diagnostics. The researchers separately analyzed how many cancers occurred in study participants after one and five years, respectively, following their hospital stays. This revealed a slightly lower risk elevation, but, the researchers concluded, the trend was the same.