If that was since you turned 18 and were there for 6 months at least, you do.
Directly from the CIC website:
"In general, you and all the people in your family who are 18 or older need to get a police certificate. You must get one from each country or territory where you have spent six or more months since the age of 18. For example:
if you visited, worked or lived in a country for two months, left for a few years, then returned for four months, that counts as spending six months there. In this case, you would need a certificate.
For the country you currently live in, the police certificate must be issued no more than six months before you apply.
For countries where you have lived for six months or more, the police certificate must be issued after the last time you lived in that country."
http://www.cic.gc.ca/english/information/security/police-cert/intro.asp
