Canada's privacy watchdog is warning marijuana users to pay with cash rather than plastic if they're worried about the collection of their personal information.

Privacy Commissioner Daniel Therrien notes that cannabis is illegal in most jurisdictions outside of Canada, and the personal information of cannabis users is, therefore, very sensitive.

Therrien suggests buyers can avoid the collection of their personal information by using cash instead of credit cards when buying pot from legal retail outlets.

However, this option is currently not available to Ontarians, who have little choice but to buy online until brick-and-mortar stores open in the spring.

Therrien says cannabis purchasers should further guard their privacy by not providing retailers with more personal information than necessary, other than what is legally required to verify their age.