The Parole Board has contacted the 38 individuals whose privacy was breached and apologised to them.
The Parole Board told 1 News that they've already fielded a number of complaints from those identified in the briefing notes.
Chairman of the New Zealand Parole Board Sir Ron Young said the organisation is taking the incident "extremely seriously".
"Every effort has been made by the Board member to locate the drive.
"The breach of privacy had no bearing on the outcome of any parole hearings as all decisions relating to the affected offenders had been made and documented prior to loss of the drive."
"As a result of this incident, I have reminded Board members the requirement to ensure all sensitive information is handled in a manner that maintains privacy and security. At the time I also alerted the Privacy Commissioner of this matter," he said.
"I am committed to ensuring the security and confidentiality of all information our members hold."