The short and confusing answer, as demosntrated by the other posts, is: both.
In common parlence a Canadian of any age will use feet and inches to describe their height. The reason for this is likely our proximity to the US and the former connection to Britain.
Canada does employ the metric system. It does so more successfully in some aspects (speed and distance and measurements) rather than others (height and weight).
In government documents (for example, a driver's licence) height will be expressed in meatric measurements, namely centimetres. For this reason, most Canadians know their height in feet and inches and many also know it is centimetres.