18 in the United States, & 16 in Europe. If you must smoke, please check out BLU E-cigs. I smoked for 12 years, and when I told my doctor that I had switched he was happy. "Better if you had quit, but it is a much healthier alternative"
In my state its the age of 18, in most states its 21. I wouldnt sugguest smoking because you will develope breathing problems from it, you will smell like an ashtray which isnt pleasant. Your teeth and your finger nails will become yellow also because of the nicotine.