Stock options from US company issued to Canadian resident

[polarys]

Hi everyone,

I have a unique situation (don't we all?) and before I go to Mr. Serbinski for advice I thought I'd throw it out to you guys to see what you think.

Here's my situation:
- I live in Canada
- I work for a Canadian corporation (which I own) with an office only in Canada
- Most of the work I do is software development contract work for a US company - I invoice the US company through my Canadian corporation and earn salary through the Canadian corporation (and pay Canadian taxes)
- Five years ago I was granted nonqualified stock options in the US company under my own name, which are now fully vested
- Since then I have also received additional grants of NQSO (partially vested)

Now my question to you is about the stock options - what are the tax implications for exercising options (and then selling either immediately or some time later)? Since I am based in Canada working for a Canadian corporation do I only have to consider Canada's tax laws in planning my strategy for options? Or do I fall under US tax laws because it's a US corporation issuing the options/shares to my own personal name?

Thanks in advance!