Trade Me dealt with 33 police inquiries relating to users in the Northland area in the year to July, according to the website's annual transparency report.
Requests can be made for member information, advice to withdraw a listing or a request to pass on educational information to a member.
The top three topics of inquiry were stolen goods, non-delivery and firearms.
The report said Trade Me worked with police to keep the site trustworthy and safe. Police helped ensure sellers who didn't deliver items were held to account.
Cruising Electronics owner Ruth White, of Northland, said her business had been selling items through Trade Me for about 12 years and the site was its main source of income. It was important that the site remained trusted.
She thought a lot of people in Northland had reasonable-sized businesses on Trade Me and the site made it possible to work away from the main centres.
Ms White said it was good that Trade Me was sharing information with police. It meant users knew that police could approach Trade Me for information about people trying to sell stolen goods or failing to send items.
She was also positive about Trade Me's annual transparency reports, making details of information sharing available.
Nationally, Trade Me received 1508 inquiries from police in the year to July. It received a further 625 requests from other government agencies, according to its transparency report.
Trade Me said other companies should also share member and customer personal information through some form of transparency reporting.
"We believe all New Zealand companies being asked to share member and customer personal information should be explaining what they do and why via some form of transparency reporting," a spokesman said.
InternetNZ deputy chief executive Andrew Cushen said Trade Me was complying with the law and doing its best to protect its customers and the New Zealand public by sharing information with police and other Government agencies.
He said those agencies asked for that sort of information from companies all the time.
"That's why these transparency reports from Trade Me are so valuable. They give New Zealanders more information and visibility and therefore confidence in using internet platforms as part of their everyday lives and business activities."
Mr Cushen said InternetNZ had produced advice encouraging other companies to adopt a similar approach in increasing their transparency around requests.
As information was increasingly being held online, companies had more of an obligation to take good care of it.
"Part of taking good care of your customers' information is disclosing where, and on what terms, you've provided that to government agencies."
He said companies that held information had a responsibility to be good stewards and government agencies had a responsibility to be reasonable in their requests for private information. Users should also be discerning about information they shared online.