YES!!! Very much so! Most doctors will say that smoking and having diabetes is like a death sentence! Diabetes greatly increases your risk of heart disease, as does smoking. It's like a double whammy on your poor body. Smoking has also been linked to an increased and earlier incidence of diabetic complications, such as kidney failure and vascular damage, which can lead to amputations.
We (as a society) all need to learn to live HEALTHILY, diabetes or not. And that means not smoking!
If your doctor has not warned you about smoking, my personal opinion is to fire him and get a new doctor.
I know it's not easy to quit, but trust me, your body will thank you. It's not fun to have a heart attack or open heart surgery at age 45. Quiting is just one of those things that needs to be done, just like controlling your blood sugars.