Ghana has in its credit of five elections since military rule ended in 1992.
Political analysts believe the stakes are higher than ever as commercial oil production that began in 2010 is expected to expand.Mr Mahama wants to spend Ghana's new wealth on large investments in infrastructure, while Mr Akufo-Addo is advocating free secondary education.
As a top exporter of cocoa and gold, Ghana is one of the world's fastest-growing economies.
Voting continued for a second day in some areas after breakdowns in a new biometric voting system meant many were unable to cast their ballots on Friday. Experts and observers say the election has been largely peaceful.Results had been expected as early as Sunday but it was unclear if the timeframe would remain after the extension.A second round is possible on 28 December if no candidate wins an outright majority.
Mr Mahama, speaking after casting his vote on Friday, said the elections would "go down in history as the best ever to be held in Ghana".
Mr Akufo-Addo expressed hope that the polls would remain peaceful.Mr Mahama took over as president after John Atta Mills died in July. His National Democratic Congress is also defending a narrow parliamentary majority. Media agencies