why are Canadian cigarette packs different ?

Because it is a different country and has different rules, laws and regulations for smoking and buying and selling cigarettes.

Well, the brands are all different for a start.  Canadians have always preferred the little box that they come in.  And, Canada has very strong anti-smoking regulations, so the boxes are printed with all sorts of warnings.

Do you know that Canada is a different country to America?

They have to put a few more in there to entice you into buying them, the last time I had a Canadian cig. I threw it away and rolled up some lawn grass instead 

Some American cigarette brands have soft packaging while Canadian packs have cardboard packaging. Apart from that cigarette packs vary in shape depending on how many cigarettes are in the pack. If Americans mainly have 20 cigarettes per pack, they will be a different shape from packs with 25, 30, 40 or 50 cigarettes.

Canadian cigarette packs also carry large health warnings as do cigarettes in many other countries. Australian packs also have plain packaging, I don't know if Canadian packs are going the same way. This means that the part of the pack not covered by a health warning is either brown or white with just the name of the brand in small letters.