More than 18,000 unwanted Christmas gifts were on the auction website Trade Me by Boxing Day.
Trade Me says items range from clothes that don't fit to DVDs, handbags and appliances.
Spokesperson Paul Ford says most people who have listed items appear to genuinely have no use for the gift.
He says a poll Trade Me carried out two years ago showed 65% of people of those questioned thought it acceptable to sell unwanted gifts.
