Team Player Som:

There is nothing that stops you from obtaining Permanent Residency of both Canada and USA. Technically, there is no difference between a VISA without any restriction and a permanent residency. Just like obtaining visas for more than one country is perfectly legal and valid, the same applies to the residency status. However there is once catch, as one of the responders mentioned above. The permanent residency comes with an implicit condition that you have full intention to live in that country for a foreseeable future. If you don't, then you should not really have obtained the permanent residency. With that in mind, the governments of these countries require that you live in those countries for a minimum period of time within 5 years period. In Canada's case, it is 2 or 3 (not sure) you must live in that country. The US is more restrictive. If you live outside of the country for more than a year consecutively, then you may lose your permanent residency. With such conditions and the reality that you have to maintain your regular business or job in the country you live, holding the two permanent residency becomes unsustainable. Hope this answers your question...

//YoTaBhayanaNiSom