Students must not have written the Putnam Competition and must meet age, full-time school enrollment, and Canadian Citizenship (or permanent residency) requirements.
Participants are invited to write the CMO usually because of excellent results at the Canadian Open Mathematics Challenge (COMC).
The organizing committee may also invite participants based on their earlier CMO experience or their performance at APMO or USAMO competitions.
In the 1970s, the exam length changed a number of times before finally stabilizing to five questions in 1979.
The CMS does not formally disclose its marking procedure, however in the past the following model was used: There are several different types of rewards for doing well on the CMO: