Depends where you're going.
www.wikipedia.org:
In Canada most of the provinces require smokers to be 19 years of age to purchase cigarettes (except for Quebec, Saskatchewan, Manitoba and Alberta, where the age is 18). However the minimum age only concerns the purchase of tobacco, not use. Alberta, however, does have a law which prohibits the possession or use of tobacco products by all persons under 18, punishable by a $100 fine.
Alcohol: 18 years of age in in Alberta, and Manitoba and Qu�bec; 19 years of age in all other provinces and in the territories.