Hi,
I am marrying to a girl who is an immigrant.Their family came to Canada ~5 yrs back.But she hasn´t yet applied for her citizenship.Would she be able to sponsor me?Would that have any effect on my application for immigration ?

What is the difference between immigrant and citizen in canada?

Please let me know.

To sponsor you, your spouse needs to be a Canadian Permanent Resident (PR)(Citizenship is not needed).

Note that not all immigrants are PRs. One can lose the PR status too.

This will be a good place for you to start:
http://www.cic.gc.ca/english/sponsor/index.html

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|CATORMTL|
Something told the wild geese
It was time to go
Though the fields lay golden
Something whispered, "Snow"
-Rachel Feld

Thanks a lot !