With almost 5000 runners taking part in Sunday's Christchurch Marathon, organisers believe it'll be a lucrative weekend for retailers.

It's the first time Christchurch has held the event since the 2010 quakes.

Most central city roads will be closed between 8.30am and 11am, and motorists are urged to use the four avenues or avoid the area.

Race director Chris Cox says it'll bring thousands of people into the city, and bring a lot of money back into the local economy.