Canadian Permanet Residency and U.S green card

Hi there,

Currently I am on EAD status in United States. My green card interview will be within couple of months. Before coming to States I was in Canada on student and work permit. 2 years back I had filed for Permanent Residency in Canada. Lately I received a letter for Medical check from CIC.
My question is can I keep the residentship of both the countries? That is United States - green card as well as Canada - Permanent Residency card? If I will receive green card earlier (just predicting) and if at all my PR gets approved, do I have to give away the Canadian permanent residency card? Any feedback is appreciated!

Later

You don't need to give back your Cdn PR card just because you get US green card. However, it is almost impossible to maintain eligibility for both cards for much more than a couple of years.
Eventually you will need to choose one or the other: by where you wnat to live most.