In Montreal, several hundred people met at the foot of Mount Royal to run up the mountain together.
A number of runners took part in last week's marathon and wore the event's official yellow and blue windbreakers.
Meanwhile, races already planned for Toronto and Vancouver have taken on extra significance.
Organizers of Vancouver's 10-kilometre race, Canada's largest road race, say registration spiked after the attack.
Tens of thousands of runners are expected compete in the city's annual Sun Run.
A total of 48,196 participants had signed up before registration closed yesterday.
A pair of bombs that exploded at the finish of the Boston Marathon killed three people and injured more than 180 last Monday.