Organisers said around 30,000 people took part in the annual New Year's Day march for democracy, while police put the figure at 11,100 -- less than half their estimate last year.
Marchers carried banners reading "Democracy will prevail" as they sang and shouted slogans against the government of the semi-autonomous Chinese city.
"Because we are Hong Kong citizens, we must vote," said Sharon Tang, a 49-year-old trading company employee, adding that residents of the former British colony have the intelligence to choose their leaders.
China, which took back Hong Kong in 1997, has promised that its people will be able to vote in 2017 for their next chief executive.
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Currently the leader is elected by a 1,200-strong pro-Beijing committee.
But many pro-democrats fear that China will control the choice of candidates to secure the election of a sympathetic official.
They say the public should have the right to nominate candidates, something which China rejects.