Custom process between US and Canada?
 

My wife is visiting me in US with a visitor visa, and she is going to Vancouver to visit her cousin next month. I have couple of questions for people who have traveled to YVR from US with a Visitor Visa.
1) Where do you hand in the I-94? Before you boarding the plane in US or after you landed in YVR.
2) When coming back, you have to go through the U.S Custom and Immigration at YVR, does this mean you don't have to go through the Custom again after you landed in US?

Thank you ver much.

I assume your wife has a multiple entry visa for the U.S. and one for Canada if applicable. Could you check that? You don't want her going to Canada and not being able to reenter the U.S. in order to return home. Also, she might want to ask an U.S. immigration/BCIS supervisor if she has to turn in her I-94 for short visits to Canada (or Mexico). It's not required for those entering under VWP.

Anyway if she has to turn her I-94 in, she hands it to the gate agents on her flight to Canada.

On here return, she does indeed preclear U.S. entry procedures at YVR and her arrival into the U.S. is considered domestic for all intents and purposes.

I think you have answered all of my questions. My wife is a Hong Kong resident and has a 10 year multiple entry visitor visa to U.S, and I believe she does not need visa to visit Canada. So it might be safer for her to hand in the I-94 and get another one on her way in.
Now I don't have to leave a lot of time for the Custom if a connection is needed inside the U.S, but any idea how much time I need to clear the custom at YVR generally?

Thank you very much terenz, I really appreciate it ^

You don't need to allow for entry into the U.S. so you can treat any connections from Canada as a domestic flight. The only exceptions that I am aware of would be the CX flight to JFK or the PR one to LAS which do not preclear.

Preclearance in YVR (check in to gate) can take anywhere from just 5 minutes or less to well over an hour or even longer! It all depends on time of day, day of week and season. I'd give it at least 1 1/2 -2 hours.