The B.C. Centre on Substance Use wants to know how, when, where and why marijuana dispensary users buy their pot.

The drug-use research centre is seeking 1,000 dispensary clients to join an online survey to examine the possible benefits and harms of dispensaries as Canada gets ready for legalization next year.

"We know [dispensaries] serve a pretty wide cross section of people in Vancouver," BCCSU researcher M-J Milloy told On The Coast guest host Gloria Macarenko.

"We also suspect they are serving people for medical and non-medical purposes. That is really why we want to do the research: to sample the full gamut of cannabis users in Vancouver to find out why they use cannabis, what the impacts are and try and prepare for legalization."

Milloy says researchers will follow up with participants after marijuana is legalized to see how the changes to the law have affected them and their pot use. He says this follow-up data will be useful for evaluating how the government approaches legalization.

"[Legalization] is the biggest experiment in drug policy in our lifetimes," he said. "So it's important we try and get it right, and as scientists, to observe what's going on."

Clients can join the online survey by getting a code from a participating dispensary.

The BCCSU says it aims to complete the first part of the survey by the end of the summer and release their findings by January 2018.

Marijuana is set to be legalized in Canada by the summer of 2018.

Listen to the full interview:

With files from CBC Radio One's On The Coast