Read this article...from the immigration website of canadian government.

http://www.cic.gc.ca/english/information/representative/index.asp


I am posting the content below:

"Immigration representatives are people who offer immigration advice or assistance to visa applicants, usually for a fee.

You do not need to hire an immigration representative. It is up to you. The Government of Canada treats everyone equally, whether they use the services of a representative or not.

If you choose to hire a representative, your application will not be given special attention by the immigration officer. Your representative also cannot guarantee that your application will be approved.

All the forms and information that you need to apply for a visa are available for free on this website. If you follow the instructions in the application guide, you can complete the application forms and submit them on your own."